Sexual differentiation: normal and abnormal

Published on 09/03/2015 by admin

Filed under Obstetrics & Gynecology

Last modified 22/04/2025

Print this page

This article have been viewed 2411 times

CHAPTER 13 Sexual differentiation

normal and abnormal

D. Keith Edmonds

Introduction

Sexual differentiation and its control are fundamental to the continuation of most species. The understanding of this process has advanced greatly in recent years, but before abnormalities of these disorders can be discussed, an understanding of normal sexual development is important. At fertilization, the haploid gametes unite and the conceptus contains 46 chromosomes with 22 autosomes derived from each of the gametes (i.e. sperm and ovum). The ovum donates one X chromosome and the sperm donates either one X or one Y chromosome; the axiom of mammalian reproduction is that a 46XX embryo will differentiate into a female, and a 46XY embryo becomes a male. It is, however, the presence or absence of the Y chromosome which determines whether the undifferentiated gonad becomes a testis or an ovary, and therefore the development of a male or female of the species.

Normal Embryological Development of the Reproductive System

Although chromosomal sex is determined at the time of fertilization, gonadal sex results from the differentiation of the indifferent undifferentiated gonad which becomes either a testis or an ovary. This begins during the fifth week of embryological development; at this time, an area of coelemic epithelium develops on the medial aspect of the urogenital ridge, and proliferation leads to the establishment of the gonadal ridge. Epithelial cords then grow into the mesenchyme (primary sex cords), and the gonad now possesses an outer cortex and an inner medulla. In XY individuals, the medulla becomes the testis and the cortex regresses. In embryos with an XX complement, the cortex differentiates to become an ovary and the medulla regresses. The primordial germ cells develop by the fourth week in the endodermal cells of the yolk sac, and during the fifth week, they migrate along the dorsal mesentery of the hindgut to the gonadal ridges, eventually becoming incorporated into the mesenchyme and the primary sex cords by the end of the sixth week (Figure 13.1).

Figure 13.1 Normal gonadal differentiation.

Development of the testis

The primary sex cords become concentrated on the medulla of the gonad and proliferate, and their ends anastomose to form the rete testis. The sex cords become isolated by the development of a capsule called the ‘tunica albuginea’ and the developing sex cords become the seminiferous tubules. Mesenchyme grows between the tubes to separate them (Leydig cells). The seminiferous tubules are composed of two layers of cells: supporting cells (Sertoli cells) derived from the germinal epithelium, and spermatogonia derived from the primordial germ cells (Figure 13.1).

Development of the ovary

The development of the ovary is much slower than that of the testis, and the ovary is not evident until the 10th week. Now, the primary sex cords regress and finally disappear. Around 12 weeks, secondary sex cords arise from the germinal epithelium, and the primordial germ cells become incorporated into these cortical cords. At 16 weeks, these cortical cords break up to form isolated groups of cells called ‘primordial follicles’; each cell contains an oogonium derived from a primordial germ cell, surrounded by follicular cells arising from the cortical cords. These oogonia undergo rapid mitosis to increase the numbers to thousands of germ cells called ‘primary oocytes’. Each oocyte is surrounded by a layer of follicular cells, the structure being called a ‘primary follicle’. The surrounding mesenchyme becomes the stroma.

Genetic control of gonadal development (Figure 13.2)

The pathway which controls the genetic interaction which transforms intermediate mesoderm to the bipotential gonad is beginning to be understood. It is now possible to identify with certainty two genes that are associated with this process. These two genes are Wilms’ tumour gene (WT1) and FTZ1. WT1 has been found on chromosome 11, p13 and regulates DNA transcriptase (Hastie 1994, Dong et al 1997). FTZ1 produces steroidogenic factor 1 (SF-1), and this has been found to be required for differentiation to the bipotential gonad (Wilhelm et al 2007).

Figure 13.2 Diagram showing genetic control of gonadal development.

As the presence of a Y chromosome is essential for testicular differentiation, the localization of testicular-determining factor (TDF) which was localized at the short arm of the Y chromosome using cloning and DNA sequencing techniques, and the gene determining TDF was sequenced and designated SRY (sex-determining region Y gene) (Guellaen et al 1984, Behlke et al 1993). The second gene which is involved in the differentiation of the testis is known as SOX9, and this gene coexists with the SRY gene in its homeobox and is a regulator of DNA transcription. SOX9 gene expression is increased in male gonadal differentiation and decreased in female gonadal differentiation. SOX9 has also recently been shown to be a regulator of type II collagen which is involved in the formation of cartilage (Lefebvre et al 1997). The DAX1 gene is responsible for development of the receptor on the surface of the undifferentiated gonad, which allows SRY and SOX9 to differentiate the gonad to become a testis. Following the development of Leydig cells and Sertoli cells, SF-1 is involved in the control of steroid hydroxylases, and P450 aromatase causes an increase in the synthesis of testosterone and a reduction in the conversion of androgens to oestrogens, leading to a contribution to testicular regulation (Ogata 2008). In combination with ST1, it is also responsible for Sertoli cells producing anti-Müllerian hormone. Following differentiation, Leydig cells produce insulin-like 3 (INSL3) gene, expression of which leads to testicular descent and shortening of the gubernaculums (Foresta and Ferlin 2004).

The genes involved in ovarian differentiation are much more difficult to define, although DAX1 expression continues during ovarian differentiation. Therefore, it is suggested that DAX1 antagonizes the actions of the SRY gene (Swain et al 1998).

Sex chromosome anomalies

Variations may occur in the number or the structure of chromosomes in a mosaic or a non-mosaic form. The non-mosiac forms are summarized in Box 13.1.

(based on data in Therman and Susman 1993 and Simpson 1999).

Intersex Disorders

Intersex disorders are best classified into three groups (see Figure 13.4). This classification was suggested by Hughes (2008) as a new simple classification which includes all disorders of intersex.

Figure 13.4 2008 classification of inter-sex disorders. DSD, disorders of sexual development.

Female (46XX) disorders of sexual development

Definition

This group of disorders comprises conditions in which masculinization of the external genitalia occurs in patients with a normal 46XX karyotype. The degree of masculinization is variable, ranging from mild clitoromegaly to complete fusion of the labial folds with a penile urethra.

Pathophysiology

The abnormalities occur when a female fetus is exposed to elevated levels of androgens. As the differentiation of the external genitalia to male or female depends on the conversion of testosterone to dihydrotestosterone (DHT) in the tissues of the cloaca, the presence of DHT leads to male-type development. If the female fetus is exposed to low levels of androgen, partial masculinization may occur, leading to ambiguous genitalia; however, if the levels are sufficiently high, complete male external genital development may occur, although the testes are naturally absent. If androgen exposure is delayed until after 12 weeks, virilization is limited to clitoral enlargement with no effect on the already differentiated labia. Androgens have no effect on internal sexual development, and therefore the ovaries, uterus and upper vagina are normally formed and functional.

Aetiology

The causes of androgenization are due to excessive androgens either:

• arising in a fetus (e.g. congenital adrenal hyperplasia);

• arising in the mother (e.g. androgen-secreting tumour); or

• ingested by the mother (e.g. progestogens, danazol).

There are also cases which are associated with other congenital abnormalities or which are idiopathic.

Congenital adrenal hyperplasia

Pathophysiology

This is the most common cause of female pseudohermaphroditism and is an autosomal-recessive disorder resulting in enzyme deficiency in the biosynthesis of cortisol in the adrenal gland. Cortisol production occurs in the zona fasciculata and zona reticularis (Figure 13.5), and is controlled by adrenocorticotrophic hormone (ACTH) secreted by the pituitary gland. Adrenal androgen production occurs in the same area and is influenced by ACTH. A deficiency in any enzyme in the pathway results in decreased production of cortisol with resultant elevated levels of ACTH. This leads to increased steroid production by the adrenal reticularis and consequent hyperplasia. The stimulation by ACTH elevates the levels of circulating androgens, and this results in virilization of the female fetus.

Figure 13.5 Adrenal synthesis of steroids.

There are three adrenal enzyme deficiencies which result in masculinization: 21-hydroxylase, 11-hydroxylase and 3β-dehydrogenase deficiency.

21-Hydroxylase deficiency

This accounts for 90% of all cases of congenital adrenal hyperplasia. The deficiency results in an increase in progesterone and 17α-hydroxyprogesterone, and this substrate is therefore converted to androstenedione and subsequently to testosterone. Failure of 21-hydroxylase to convert progesterone to 11-deoxycorticosterone may result in aldosterone deficiency; this occurs in approximately two-thirds of cases and is the so-called ‘salt-losing’ type of congenital adrenal hyperplasia.

Aetiology

Deficiency of 21-hydroxylase is an autosomal-recessive disorder. The link between human leukocyte antigen (HLA) type and 21-hydroxylase deficiency was established by Dupont et al (1977), and this allowed mapping of the gene which was located on the short arm of chromosome 6. It is located between the HLA-B and HLA-DR loci, and subgroups of HLA-B have been closely linked to congenital adrenal hyperplasia type: HLA-BW47 is linked to salt-losing congenital adrenal hyperplasia and HLA-BW51 is linked to the simple virilizing form. Studies by Donohoue et al (1986) have shown that there are two 21-hydroxylase genes: 21-OHA and 21-OHB. Only one is active (21-OHB) and they both lie between the fourth components of complement C4A and C4B. A variety of mutations have been reported, including gene deletions of 21-OHB, gene conversions and point mutations.

Epidemiology

The incidence of 21-hydroxylase deficiency is between one in 5000 and one in 15,000, based on neonatal screening programmes (Cacciari et al 1983), although a higher incidence (one in 700) has been reported in specific populations of Eskimos (Pang et al 1982). The incidence of the non-classic form of the disease, when androgenization fails to appear before late childhood or puberty, is much more common; approximately one in 300 in the White population and one in 30 in European Jews (Pang et al 1988).

Presentation

Affected females are born with an enlarged clitoris, fused labioscrotal folds and a urogenital sinus which may become a phallic urethra. There is often great variation in the degree of masculinization of the external genitalia; this is classified according to Prader (1958).

The internal genitalia develop normally as they are not influenced by androgens.

In salt-losing congenital adrenal hyperplasia, the infants develop dehydration, hypotension and hyponatraemia between 7 and 28 days of age, known as a ‘salt-losing crisis’. Non-salt-losing congenital adrenal hyperplasia tends to cause less severe masculinization than the salt-losing type. In general, all children born with ambiguous genitalia, including cryptorchidism and hypospadias, should be screened for congenital adrenal hyperplasia. Without treatment, severe salt-losing disease is fatal.

When an infant is born with ambiguous genitalia, the management of the parents is very important. It is helpful to reassure them that the infant is healthy and that there is a developmental anomaly of the genitalia. If the initial examination of the child fails to identify palpable gonads, it is most likely that the child is female and the parents should be informed as such; the likelihood of congenital adrenal hyperplasia may be raised. The diagnosis must then be made with as much haste as possible to alleviate parental anxiety.

Investigation

The initial investigations are karyotyping, pelvic ultrasound and endocrine studies. The karyotype may be performed on a sample of cord blood or on a venous sample, and rapid results obtained. Pelvic ultrasound to discover the presence of a uterus and vagina will confirm the diagnosis. The specific diagnosis is made by measuring 17α-hydroxyprogesterone in serum, although a 24-h urinary estimate of 17-ketosteroids will also confirm the diagnosis.

Treatment

This is divided into four parts.

Acute salt-losing crisis

This involves correcting the electrolyte imbalance and replacing the cortisol deficiency with deoxycorticosterone acetate (DOCA), 1 mg/24 h. For the majority of cases, 9α-fludrocortisol is used at a dose of 0.1–0.2 mg/day added to the oral feed, and the dosage of DOCA or fludrocortisol is adjusted against the electrolyte levels.

Long-term cortisol replacement therapy

Although previous reports suggested that mineralocorticoid therapy could be discontinued after infancy (Newns 1974), more recent data suggest that it is essential to continue therapy for life (Hughes et al 1979).

Surgical correction

Once the sex of rearing has been established as female, some attempt to feminize the genitalia may be made, usually within the first 18 months of life. If the clitoris is enlarged, a reduction clitoridectomy can be performed and the perineal region modified (Edmonds 1989). There are major surgical problems associated with severe virilization in congenital adrenal hyperplasia. The urogenital sinus has been formed by labial fold fusion and the folds are usually thin, but may be thick with associated narrowing of the lower vagina, especially in salt-losers. If the labial folds are thin, division by a simple posterior incision may be performed around 3 or 4 years of age. However, thick perineal tissue should be left until after puberty, and no attempt at surgery should be made until the girl is physically and mentally sexually mature. The operation, when it is performed, involves a flap vaginoplasty with a pedicle graft of labia used to recreate the vagina. Alternatively, a Williams vaginoplasty may be used.

Mulaikal et al (1987) reviewed the fertility rates in 80 women with 21-hydroxylase deficiency; of 25 with the simple form who attempted pregnancy, 15 were successful, whereas only one of the salt-losers who tried to become pregnant succeeded. There is no doubt that a major reason for the failure of the salt-losing group is the disappointing results of surgery and subsequent lack of adequate sexual function.

Psychological support

As the child grows, long-term psychological guidance and support will be required for the parents initially and then the child.

Prenatal diagnosis

If the parents are heterozygous carriers of 21-hydroxylase deficiency, the fetus has a one in four chance of being affected. Thus, prenatal diagnosis is important, either by amniocentesis to measure levels of 17-hydroxyprogesterone in amniotic fluid, HLA typing of amniotic cells, or chorionic villus sampling and the use of specific DNA probes. Once the diagnosis has been made, the option is available to treat the pregnant woman with oral dexamethasone, which crosses the placenta and suppresses the secretion of ACTH and thus the circulating androgen levels.

11-Hydroxylase deficiency

This is the hypertensive form of congenital adrenal hyperplasia which accounts for approximately 5–8% of all cases (Zachmann et al 1983). The absence of 11-hydroxylase leads to elevated levels of 11-deoxycorticosterone (DOC), and although this means a decreased amount of aldosterone, DOC has salt-retaining properties, leading to hypertension. Androstenedione levels are also elevated and this can result in ambiguous genitalia.

The diagnosis is made by measuring elevated levels of urinary 17-hydroxycorticosteroids and raised serum androstenedione. Treatment is similar to 21-hydroxylase deficiency, with glucocorticoid replacement therapy.

The genetics, however, are rather different. There is no HLA association with 11-hydroxylase deficiency, but the use of a DNA probe has located the gene on the long arm of chromosome 8 (White et al 1985).

3β-Dehydrogenase deficiency

This rare form of congenital adrenal hyperplasia results in a block of steroidogenesis very early in the pathway, giving rise to severe salt-losing adrenal hyperplasia. The androgen most elevated is dehydroepiandrosterone, an androgen which causes mild virilization. The diagnosis rests on the measurement of elevated dehydroepiandrosterone. The gene encoding 3β-dehydrogenase has not yet been cloned but it is not linked to HLA.

Androgen-secreting tumours

Androgen-secreting tumours are rare in pregnancy, but may arise in the ovary or the adrenal gland. They cause fetal virilization. When they occur in the non-pregnant woman, anovulation is induced.

Ovary

A number of androgen-secreting tumours have been reported, including luteoma (Hensleigh and Woodruff 1978, Cohen et al 1982), polycystic ovaries (Fayez et al 1974), mucinous cystadenoma (Novak et al 1970, Post et al 1978), arrhenoblastoma (Barkan et al 1984) and Krukenberg tumours (Connor et al 1968, Forest et al 1978). Not all female fetuses will be affected and there is no association with gestation and exposure. The fetus may be partly protected by the conversion of the maternally derived androgen to oestrogen in the placenta, and thus the degree of virilization is variable.

Adrenal gland

There are only two reports of adrenal adenomas causing fetal masculinization (Murset et al 1970, Fuller et al 1983). These tumours may be responsive to human chorionic gonadotrophin, and thus levels of androgen may be higher in pregnancy than in the non-pregnant state, leading to androgenization of the fetus.

Drugs

The association between the use of progestogens and masculinization of the female fetus has received much publicity, but the only progestogen proven to have such an effect is 17-ethinyl testosterone (Ishizuka et al 1962). These infants had clitoromegaly and, in some cases, labioscrotal fusion, but the risk is very small (one in 50). Gestogens which are derived from testosterone should be avoided in the pregnant woman. There have been two case reports of androgenization of female fetuses from exposure to danazol during pregnancy (Castro-Magana et al 1981, Duck and Katamaya 1981), and both babies were born with external genitalia similar to those with adrenogenital syndrome.

Associated multiple congenital abnormalities

Female intersex has been described in association with a number of multiple abnormality states, most commonly those in association with the urinary and gastrointestinal tracts. It has also been described in association with VATER (Vertebrae, Anus, Trachea,Oesophagus and Renal) syndrome (Say and Carpentier 1979).

The management of these children with masculinized genitalia is to ensure the assignation of a sex of rearing, and to modify the genitalia appropriately. In all of these rare cases, the female role has been chosen and reduction clitoroplasty performed.

46XY Disorders of Sexual Development

The normal differentiation of the gonad to become a testis has been described above, and its subsequent secretion of testosterone leads to development of the Wolffian duct and the urogenital sinus to produce the normal male internal and external genitalia. Testosterone is the predominant male sex hormone secreted by the testis, but two other processes are necessary for normal development: the conversion of testosterone to DHT by 5α-reductase, and the presence of androgen receptors in the target cell which bind with the DHT or testosterone and produce appropriate nuclear function. Thus, a normal male genotype (i.e. XY) with a female phenotype will occur if there is:

• failure of testicular development;

• error(s) in testosterone biosynthesis; or

• androgen insensitivity at the target site.

Failure of testicular development

This group of disorders includes true gonadal dysgenesis, Leydig cell hypoplasia and the persistent Müllerian duct syndrome.

True gonadal dysgenesis

True gonadal dysgenesis is characterized by streak gonads, normal Müllerian structures and normal external female genitalia. It has been suggested that the streak gonads in these individuals were originally ovaries which contained oogonia which then subsequently underwent massive atresia, in a similar fashion to Turner’s syndrome. The karyotype is either 46XY or 46XX, and these patients usually present in their teenage years with failure of pubertal development.

46XY partial gonadal dysgenesis

In this condition, the infants are born with ambiguous genitalia, which results from the partially dysgenetic development of the testis. The dysgenetic gonads have various histological arrangements, with poor seminiferous tubules. However, some androgen can be produced by these testes, which results in partial androgenization of the external genitalia, leading to the genital ambiguity. These children have a high risk of gonadal tumours, especially gonadoblastoma, and in these circumstances, the gonads should be removed early to prevent this development.

Leydig cell hypoplasia

Leydig cell hypoplasia is an uncommon condition of which the aetiology remains speculative. The role of fetal luteinizing hormone in normal testicular development is unknown, but it may be necessary for maturation of the interstitial cells into Leydig cells. Failure of luteinizing hormone production in the first trimester will result in Leydig cell hypoplasia and male pseudohermaphroditism (or an autosomal-recessive disorder resulting in absent luteinizing hormone receptors will cause absence of Leydig cells). This manifests as ambiguous genitalia, in both circumstances due to some androgen production by Sertoli cells. Clinically, Leydig cell hypoplasia usually presents as a phenotypical female with primary amenorrhoea and sexual infantilism, but ambiguity at birth may result in diagnosis in infancy.

46XY true hermaphroditism

These individuals have the presence of both testicular and ovarian tissue with a 46XY karyotype. It has been suggested that mutation of the SRY gene may be the aetiology of this (Berkovitz and Seeherunvong 1998).

46XX sex reversal

This nomenclature is used to describe the situation in which testicular tissue develops in someone with a 46XX karyotype. If testicular development is normal, they are referred to as ‘46XX males’, but when testicular determination is incomplete, they are referred to as ‘46XX true hermaphrodites’. In 46XX males, the external genitalia are usually normal or a small percentage may have hypospadias. Clinically, they do not present until puberty, when this is delayed due to failure to be able to produce testosterone and due to the degeneration of seminiferous tubules and Leydig cell hyperplasia, which seems to occur just prior to puberty. It seems that in the majority of these individuals, the sex reversal is related to the translocation of Y chromosome sequences, including the SRY gene from the paternal Y chromosome to the paternal X chromosome (Tomomasa et al 1999). However, one-third of individuals are not found to have Y chromosome sequences in their DNA, and this means that there must be a mutation in the genomic DNA which permits testicular determination to occur in the absence of TDF. These gene defects remain to be explained.

Errors in testosterone biosynthesis

This type of disorder accounts for only 4% of XY females, and results from deficiency of an enzyme involved in testosterone synthesis (see Figure 13.5).

20,22-Desmolase deficiency

Absence of this enzyme results in failure to convert cholesterol to pregnenolone, and a failure of subsequent steroid production. Most of the reported cases have died in early childhood due to adrenal insufficiency, but the XY individuals are all partially virilized with a small blind vaginal pouch. It is considered to be an autosomal-recessive disorder.

3β-Hydroxysteroid dehydrogenase deficiency

This is a rare disorder which affects both adrenal and gonadal function and is again autosomally recessive. The deficiency may be complete or incomplete, and thus the degree of virilization is variable, with various degrees of hypospadias or a small blind vagina with normal internal male genitalia and absent Müllerian structures. Those individuals who have survived and reached puberty have developed gynaecomastia, presumably because the absence of testosterone during fetal life has allowed breast bud development. The diagnosis is made by elevated levels of pregnenolone and 17-hydroxypregnenolone, and low levels of corticosteroids and testosterone.

17α-Hydroxylase deficiency

This syndrome produces a phenotype in XY individuals varying from normal female external genitalia and a blind vaginal pouch to hypospadias with a small phallus. The diagnosis is usually only made in adulthood with failure to develop secondary sexual characteristics. The impaired adrenal production of cortisol is not associated with clinical symptoms as the elevated levels of corticosterone compensate. The gonads should be removed if the patient is assigned a female gender and hormone replacement therapy instituted.

17,20-Desmolase deficiency

This enzyme defect primarily affects testosterone production and there is no adrenal insufficiency. The clinical findings range from normal female to undervirilized male genitalia, and the endocrine findings are of very low serum levels of testosterone with normal corticosteroids. Again, diagnosis may not be made until failure of pubertal development.

17-Ketosteroid reductase deficiency

This enzyme is responsible for the reversible conversion of androstenedione to testosterone and oestrone to oestradiol. These patients almost always present at birth with female external genitalia and testes in the inguinal canal, and undergo masculinization at puberty. Those individuals to be raised as females should have their gonads removed before puberty and oestrogen therapy started at puberty.

Androgen insensitivity at the target site (Table 13.1)

In this group of patients, testicular function is normal and circulating levels of androgen are consistent with normal male development. The majority of patients present at puberty with primary amenorrhoea, but some will present with ambiguous genitalia. The defect may be 5α-reductase deficiency or complete or partial androgen insensitivity.

Table 13.1 Types of androgen insensitivity and their abnormalities

5α-Reductase deficiency

This results in failure of the conversion of testosterone to DHT in target tissues and thus a failure of masculinization of the site. In infancy, there is usually a small phallus, some degree of hypospadias, a bifid scrotum and a blind vaginal pouch. The testes are found either in the inguinal canal or in the labioscrotal folds, and Müllerian structures are absent. At puberty, elevated levels of androgen lead to masculinization, including an increase in phallic growth, although this remains smaller than normal. Seminal production has been reported (Petersen et al 1977).

It is an autosomal-recessive trait and the resulting enzyme defect gives predictable hormone profiles with normal levels of testosterone but low levels of DHT. The diagnosis is important in individuals born with ambiguous genitalia in order to assign the sex of rearing, and this should be based on the potential for normal sexual function in adult life. The gonads should be removed if the sex of rearing is to be female, and oestrogen replacement therapy is instituted at puberty.

Complete androgen insensitivity

This is an X-linked recessive disorder characterized by the clinical features of normal female external genitalia, a blind vaginal pouch, and absent Müllerian and Wolffian structures. The testes are found either in the labial folds, the inguinal canal or may be intra-abdominal.

These patients may lack the androgen receptor and may be shown to lack the gene located on the X chromosome between Xp11 and Xq13. Work by Brown et al (1982), however, suggests that there may be a variety of defects, ranging from absence of receptors to presence of a normal number of receptors which are inactive. The exact mechanism of the defects in patients with androgen receptors awaits definition.

The hormonal levels of testosterone which are elevated above normal due to increased luteinizing hormone production and the associated increase in testicular oestradiol and peripheral conversion of androgens to oestradiol promotes some breast development. Pubic hair growth depends on the degree of insensitivity but is usually rather scanty.

Patients either present with a hernial mass or with primary amenorrhoea despite secondary sexual characteristics; karyotyping makes the diagnosis. The gonads should be removed because of the malignant potential. The vagina may be of variable length and may be adequate, but those with a short vaginal pouch may need manual dilatation.

Partial androgen insensitivity

This is a complex condition which has been found to be due to a reduced binding affinity of DHT to the receptor or because the receptor binds the DHT but there are defects in the transcription to the nucleus. It is an X-linked recessive disorder and the partial expression means inevitable ambiguous genitalia with a blind vaginal pouch and phallic enlargement. The penis can be normal. The Wolffian ducts can be rudimentary or normal, but the testes are azoospermic. The most common presentation in infancy is hypospadias, with the urethra opening at the base of the phallus, and there may be cryptorchidism. At puberty, male secondary sexual characteristics develop poorly, but there is usually gynaecomastia. The management is dependent on the degree of ambiguity and subsequent choice of sex of rearing, with gonadectomy and hormone replacement therapy for those assigned a female role.

Anomalous Vaginal Development

When the vagina does not develop normally, a number of abnormalities have been described. The vagina may be partially maldeveloped, leading to a vaginal obstruction which may be complete or incomplete, or there may be total maldevelopment of the Müllerian ducts leading to various disorders.

Classification

Vaginal anomalies may be categorized as follows:

• congenital absence of the Müllerian ducts (the Mayer–Rokitansky–Kuster–Hauser syndrome);

• disorders of vertical fusion; and

• failure of lateral fusion.

Aetiology

Three mechanisms explain most vaginal anomalies. They may be familial; for example, XY females who have a hereditary disorder as described previously. Congenital absence of the vagina has been very rarely reported in XX siblings (Jones and Mermut 1974), and also in monozygotic twins with only one child affected (Lischke et al 1973).

The case of a female-limited autosomal-dominant trait was first reported by Shokeir (1978) who studied 16 Saskatchewan families in which there was a proband with vaginal agenesis. However, Carson et al (1983), in a study of 23 probands, disputed Shokeir’s theory. The previous evidence with regard to monozygotic twins also makes this mode of inheritance unlikely. Polygenic or multifactorial inheritance does, however, offer some explanation that families may exhibit the trait as reported. The recurrent risk of a polygenic multifactorial trait in first-degree relatives is reported to be between 1% and 5%.

Finally, it is possible that Müllerian duct defects could be secondary to teratogens or other environmental factors, but no definite association has been demonstrated.

Epidemiology

The incidence of vaginal malformations has been variously estimated at between one in 4000 and one in 10,000 female births (Evans et al 1981). The infrequency of this anomaly makes accurate estimates of the true incidence very difficult to obtain, but when considered as a cause of primary amenorrhoea, vaginal malformation ranks second to gonadal dysgenesis.

Pathophysiology

The pathophysiology of vaginal absence may be either as a result of failure of the vaginal plate to form or failure of cavitation. Absence of the uterus and fallopian tubes indicates total failure of Müllerian duct development, but in the Rokitansky syndrome, the uterus is often present, although rudimentary, and therefore it must be failure of vaginal plate formation and subsequent vaginal development which leads to the absent vagina. Vertical fusion defects (Figure 13.6) may result from failure of fusion of the Müllerian system with the urogenital sinus, or may be due to incomplete canalization of the vagina. Disorders of lateral fusion are due to the failure of the Müllerian ducts to unite, and may create a duplicated uterovaginal septum which may be obstructive or non-obstructive, depending on the mode of development (Figure 13.7).

Figure 13.6 Disorders of vertical fusion.

Figure 13.7 Lateral fusion defects.

Presentation

Vaginal atresia

Vaginal atresia presents at puberty with complicated or uncomplicated primary amenorrhoea. In the majority who have an absent or rudimentary uterus, uncomplicated primary amenorrhoea is the presenting symptom, but those women who have a functional uterus may develop an associated haematometra and present with cyclical abdominal pain. If a haematometra does develop, there will be uterine distension and an abdominal mass may be palpable, but more commonly, it is felt on rectal examination.

Vertical fusion defects

Here, the transverse vaginal septum prevents loss of menstrual blood and therefore cryptomenorrhoea results. Most patients present as teenagers with cyclical abdominal pain, and a haematocolpos will be palpable within the pelvis on rectal examination. The patient may also present with associated pressure symptoms of urinary frequency and/or retention. The incidence of vertical fusion defects is reported as 46% high, 35% mid and 19% low septae in the vagina (Rock et al 1982).

Disorders of lateral fusion

These patients usually present with the incidental finding of a vaginal septum which is usually asymptomatic. It may first be diagnosed during pregnancy, at which time excision will be necessary to ensure a vaginal delivery. However, these patients may present with dyspareunia caused by the septum, and in most cases, one vagina is larger than the other and intercourse may have occurred partially successfully in the larger side. In the unilateral vaginal obstruction group, presentation is usually with abdominal pain and the associated symptoms of a haematometra and haematocolpos. The confusing clinical sign is the associated menstruation from the other side, and the diagnosis may be missed if careful examination is not performed in these teenagers.

Investigation

Vaginal atresia

A patient presenting with a clinically absent vagina and no cyclical abdominal pain requires an ultrasound examination of the pelvis to determine the presence or absence of a uterus and/or a haematometra. Laparoscopy in these patients is unnecessary. Some 15% of patients with the Rokitansky syndrome suffer major defects of the urinary system, including congenital absence of a kidney; 40% of patients also have trivial urinary abnormalities (d’Alberton et al 1981). It is therefore important to perform an intravenous urogram in order to establish any abnormalities in the renal system or the presence of a pelvic kidney, which may alert the surgeon to take extra care if abdominal surgery becomes necessary.

Anomalies of the bony skeleton occur in approximately 12% of patients. These include abnormalities of the lumbar spine, the cervical vertebrae and the limbs. However, it may be that the incidence of bony abnormalities is higher than this, as investigation of the skeletal system is rarely performed.

Transverse vaginal septum

Investigations in these patients are limited to ultrasound assessment of the uterus for the detection of a haematometra and haematocolpos, and this may also be used to assess the level of the septal defect. Again, investigation of the urinary tract is pertinent.

Lateral fusion defects

Investigations in this group are only important if there is an obstructed outflow problem, and should follow those outlined for vertical fusion defects.

Treatment

Vaginal atresia

The patient with Müllerian agenesis requires careful psychological counselling and associated therapy. The psychological impact of being informed of an absent vagina comes as an immense shock to both patient and parents. It is almost always followed by a period of depression in which many patients question their femininity and look upon themselves as abnormal females. They very much doubt their ability to enter a heterosexual relationship which will be lasting, and feel worthless both sexually and certainly as regards being a reproductive partner. In some patients, the depression can be very profound and suicide may be threatened. There is also great maternal anxiety over the aetiology, as most mothers feel that they are responsible for the abnormality. Reassurance of the mother is as important as that of the daughter in the management of the patient.

Occasionally, cultural problems arise which make management much more difficult, especially in ethnic groups where the ability to procreate is fundamental to marriage and social acceptance. These patients and their parents can be very difficult to console and often refuse to accept the situation, questioning the diagnosis of their sterility over a number of years. The immediate reaction of most patients is to request surgical correction of the abnormality to return them to ‘normal’. Unfortunately, opting for surgical treatment without adequate psychological and physical preparation inevitably leads to disaster. The author recommends a minimum of 6 months of preparation before any surgical procedure is performed, and during this time, psychological support can be implemented for the patient and her parents. There are two major areas of support required: first, the correction of the loss of esteem and inevitable depression; repeated counselling sessions by trained personnel are required if these symptoms are to be overcome. The second problem involves the psychological aspect; again, prolonged counselling sessions will be required if an adequate and fulfilling sex life is going to be possible in the future. The sexual life achieved by well-managed patients can be excellent and has been reported to be comparable to that of the normal population (Raboch and Horejsi 1982, Poland and Evans 1985).

Management of the absent vagina with a non-functioning uterus

In a patient with an absent or rudimentary uterus, the creation of a vaginal passage may be non-surgical or surgical. The non-surgical technique involves the repeated use of graduated vaginal dilators over a period of 6–12 months. A vaginal dimple of at least 1 cm is necessary for this technique to succeed, and patients require support and encouragement during this time. Patients are instructed to begin with a small vaginal dilator which is pressed firmly against the vaginal dimple for a period of some 20 minutes twice a day. Pressure is exerted but pain should be avoided, and repeated use of these vaginal dilators will meet with success in approximately 90% of cases with appropriate selection (Broadbent et al 1984, Edmonds 2003). This technique was first described by Frank in 1938, and in view of its undoubted success, with no complications, this method must be attempted in all girls with an absent vagina and a 1 cm dimple before any surgical procedure is considered.

In girls with a vaginal dimple of less than 1 cm or those in whom Frank’s procedure fails, vaginoplasty will be required. There are currently three techniques in popular usage: the McIndoe–Reed operation, the amnion vaginoplasty and the Williams vulvovaginoplasty.

The McIndoe–Reed procedure was first described in 1938 (McIndoe and Banister 1938) and involved the use of a split-thickness skin graft over a solid mould; this mould is placed in a surgically created space between the urethra and the rectum. This space is created digitally following a transverse incision in the vaginal dimple. Digital exploration of the space must be performed with great care as damage to the bladder or the rectum may occur. The space created must reach the peritoneum of the pouch of Douglas if an adequate length of a vagina is to be created. A split-thickness skin graft is then taken from a donor site and an appropriately sized mould is chosen. The skin graft is then fashioned over the mould with the external skin surface in apposition to the mould. The skin-covered mould is then placed in the neovaginal space, and the labia are sutured together to hold the mould in situ. McIndoe reported his own series of 105 patients in 1959 and had a satisfactory outcome in 80% of patients. Cali and Pratt (1968) reported on their series of 123 patients; 90% had good sexual function but 6% had major complications which were primarily fistulae, and subsequent reconstructive surgery was necessary in 8%. These complications resulted in modifications of the technique and the use of a soft material for the mould to prevent fistula formation due to pressure necrosis.

The search for an alternative material to line the neovagina and avoid the scarring of the donor skin site led to the use of amnion for the vaginoplasty procedure (Ashworth et al 1986). The technique involves the creation of a neovaginal space in the same way as described for the McIndoe–Reed procedure, but amnion obtained at the time of elective caesarean section is used to line the neovagina. The mesenchymal surface of the amnion is placed against the new vaginal surface to promote epithelialization, and the mould is kept in situ for 7 days and then replaced with a new amnion graft for a further 7 days. Subsequently, patients are encouraged to use dilators on a frequent basis to maintain the vaginal passage. Again, reported success of approximately 90% has been achieved by these authors.

The Williams vulvovaginoplasty (Williams 1976) has almost no place in the management of these disorders, and is much less frequently used than in the past. In patients in whom dissection of a neovagina is impossible but the labia majora are normal, this technique is valuable. The principle of the operation is to create a vaginal pouch from the full-thickness skin flaps created from the labia majora, which are united in the midline. Following surgery and adequate healing, the patient is taught to use vaginal dilators in the same way as described in the Frank technique. There is no doubt that this does allow the patient and her partner to enjoy a sex life with mutual orgasm, but the angle of the vagina is unnatural and unsatisfactory for some patients. Although the operation is simple to perform, the psychological problems of the distorted external genitalia can be considerable.

The absent vagina with a coexistent functional uterus

This situation presents major problems, as the release of menstrual blood and the relief of associated pain are the primary aims; the creation of a normal vagina is an equally important yet secondary role. The functional uterus may be normal and a cervix may be present or absent. This situation is very rare; an operation to create a neovagina in an attempt to reanastomose a uterus which has been drained of its haematometra is highly specialized and will not be discussed further.

Complications

Some 25% of women will have some degree of dyspareunia following a vaginoplasty (Smith 1983). This is most commonly due to scarring at the upper margin of the vagina, involving the peritoneum. Similar incidences of dyspareunia occur in nearly all series and it is difficult to know how best to avoid this. It seems to occur regardless of technique, but contraction of the upper part of the vagina is difficult to avoid. The artificial vagina created in these ways acquires all the characteristics of normal vaginal epithelium, and the exposure of the grafted epithelium to a new environment means that care has to be taken to ensure it remains healthy. Four cases of intraepithelial neoplasia in neovaginas have been reported (Jackson 1959, Duckler 1972, Rotmensch et al 1983, Imrie et al 1986).

Management of disorders of vertical fusion

In these abnormalities, the type of procedure is governed by the type of abnormality. In the obstructed hymen, the procedure is extremely simple and a cruciate incision through the hymen will release the accumulated menstrual blood and resolve the problem. In obstructing transverse vaginal septae in the lower and middle thirds, surgical removal of the septum can almost always be performed transvaginally, and a reanastomosis of the upper and lower vaginal segments may be performed. Great care must be taken to ensure that the excision is adequate or a vaginal stenosis at the site of the septum will remain a problem. The high vaginal septum is the most difficult abnormality to manage, and it is almost always necessary to perform a laparotomy in order to expose the haematometra. The passage of a probe through the uterine cavity and cervix into the short upper vagina allows a second vaginal surgeon to explore the vagina from below and excise the septum. The absent portion of vagina is usually so great that reanastomosis of the vaginal mucosa cannot be achieved, and either a soft mould is inserted and granulation allowed to occur, or an amnion-covered soft mould should be inserted to promote epithelialization. Vaginal dilatation following removal of the mould must be encouraged in order to prevent constriction of the new vaginal area.

Results

The results of surgery are extremely good when judged by sexual satisfaction. However, Rock et al (1982) reported pregnancy success following surgical correction of transverse vaginal septa, and noted that patients with a transverse vaginal septum had only a 47% pregnancy rate when the site of the septum was taken into account. If the obstruction was in the lower third, all patients achieved a pregnancy, compared with 43% in the middle third and 25% in the upper third. It is suggested that the difficulties in conceiving may be secondary to the development of endometriosis, and the higher the site of the septum, the more likely the development of this disorder may be. Thus prompt diagnosis and surgical correction are important in an attempt to preserve the maximum reproductive capacity in these patients.

Complications

Complications are primarily those of dyspareunia and failure of pregnancy, as described above.

Disorders of lateral fusion

The treatment of this condition depends on the abnormality in patients with a midline septum and no other abnormality; excision of the septum should be performed and care must be taken as these septa can be very thick and removal can be rather difficult. When resecting the septum, generous pedicles should be taken to ensure haemostasis, and the results are extremely good as the remaining tissue usually retracts and causes no problem. In patients in whom there is an incomplete vaginal obstruction, the septum needs to be removed and care must be taken to remove as much of it as possible. Failure to do this will result in healing of an ostium and repeat obstruction of the hemivagina. The results and outlook for these patients are extremely good.

Malformations of the Uterus

Classification and pathophysiology

There have been numerous classification systems for uterine malformations, varying from those based on embryological development to those based on obstetric performance. However, the most widely used classification is that of Buttram and Gibbons (1979), which is based upon the degree of failure of normal development. Six categories are described:

• Class I: Müllerian agenesis or hypoplasia;

• Class II: unicornuate uterus;

• Class III: uterus didelphis;

• Class IV: uterus bicornuate;

• Class V: septate uterus; and

• Class VI: diethylstilboestrol (DES) anomalies.

Many of these uterine malformations are shown in Figure 13.8.

Figure 13.8 Varieties of uterine anomalies.

A separate class of uterine malformations has been identified in the presence of communication between two separate uterocervical cavities.

The pathophysiology of failure of normal union of the Müllerian ducts is not clear. As proposed in the section on vaginal agenesis, the hypothesis of teratogens has been suggested but unsupported by evidence. It is most likely that this is a polygenic or multifactorial inheritance which slightly increases the risk of a uterovaginal abnormality arising in a family with no anomalies.

Incidence

The incidence of uterine anomalies is difficult to define as it depends entirely upon the interest of the investigator and the diligence with which investigation is pursued. Obstetric series show an incidence of uterine abnormalities ranging from one in 100 to one in 1000 (Semmens 1962). In an infertile population, the incidence increases to approximately 3% (Sanfillippo et al 1978). It is likely that the incidence of uterine malformations is greatly overestimated, as no gynaecological or reproductive problems are ever experienced in the vast majority of patients.

Presentation

Abnormal uterine development may be symptomatic or asymptomatic. The most common clinical situations that will lead to a diagnosis of malformation of the uterus are recurrent pregnancy loss, primary infertility, urological abnormalities, menstrual disorders and DES exposure.

Recurrent pregnancy loss

Recurrent pregnancy wastage in the form of abortion or premature labour is a common way in which uterine anomalies will be discovered. The role of uterine anomalies in pregnancy wastage is discussed in Chapter 21 on female infertility and Chapter 23 on recurrent miscarriage.

Primary infertility

Uterine abnormalities may be discovered during investigation of an infertile woman. However, the relationship between infertility and uterine abnormalities remains controversial.

Urological abnormalities

Not uncommonly, urologists who discover malformations of the urinary system investigate the genital system and find abnormalities. Thompson and Lynn (1966) reported that 66% of patients with a maldevelopment of the renal tract had an associated Müllerian duct abnormality. However, only 13.5% of women with anomalous renal development had anomalous uterine development. In patients with a single kidney, the most common uterine abnormality is uterus didelphis with a vaginal septum which is associated with unilateral occlusion.

Menstrual disorders

Uterine abnormalities may be responsible for a number of menstrual disorders including oligomenorrhoea, dysmenorrhoea and menorrhagia. The specific menstrual symptoms will depend on the anomaly. In an interesting study by Sorensen (1981), investigating infertile women with oligomenorrhoea, 56% of patients were found to have mild uterine abnormalities. Sorensen suggested that this oligomenorrhoea might be due to poor vascularization or steroid receptor development in the malformed uterus. With regard to dysmenorrhoea, uterine abnormalities seem to be associated with a higher incidence of primary dysmenorrhoea, although this may also be associated with obstructed outflow problems. Rudimentary hemiuteri may also be the cause of dysmenorrhoea in some women.

Diethylstilboestrol exposure

The malformations associated with DES exposure have been well described (Kaufman et al 1980). These abnormalities include a classic T-shaped uterus with a widening of the interstitial and isthmic portions of the fallopian tubes and narrowing of the lower two-thirds of the uterus, as well as non-specific uterine abnormalities with changes of cavity seen on hysterosalpingography. These patients may present with impaired reproductive function, and pregnancy wastage may be as high as 50–60%. However, as DES exposure was terminated in 1970, almost all of these individuals will now have finished their reproductive performance.