Skin Dimples

Cutaneous depressions over bony prominences and in the acral area, at times associated with pits and creases, may occur in normal children and in association with dysmorphologic syndromes. Skin dimples may develop in utero as a result of interposition of tissue between a sharp bony point and the uterine wall, which leads to decreased subcutaneous tissue formation.

Dimples may also be present overlying an area of bone hypoplasia. Bilateral acromial skin dimples are usually an isolated finding, but they are also seen in association with deletion of the long arm of chromosome 18. Dimples tend to occur over the patella in congenital rubella, over the lateral aspects of the knees and elbows in prune-belly syndrome, on the pretibial surface in campomelic dwarfs, and in the shape of an H on the chin in whistling-face syndrome.

Sacral dimples are common and usually are isolated findings. They may be seen in multiple syndromes or in association with spina bifida occulta and diastomyelia. Association with a mass or other cutaneous stigma (hair, aplasia cutis, hemangioma) should increase concern for underlying spinal dysraphism (Chapter 585). Ultrasonography during the first 3 mo of life, before ossification of the posterior elements of the lower spine, may provide a cost-effective, noninvasive method of assessing any associated lumbosacral spine abnormalities.

Redundant Skin

Loose folds of skin must be differentiated from a congenital defect of elastic tissue or collagen such as cutis laxa, Ehlers-Danlos syndrome, or pseudoxanthoma elasticum. Redundant skin over the posterior part of the neck is common in the Turner, Noonan, Down, and Klippel-Feil syndromes and monosomy 1p36; more generalized folds of skin occur in infants with trisomy 18 and short-limbed dwarfism.

Amniotic Constriction Bands

Partial or complete constriction bands that produce defects in extremities and digits are found in 1/10,000-1/45,000 otherwise normal infants. Constrictive tissue bands are caused by primary amniotic rupture, with subsequent entanglement of fetal parts, particularly limbs, in shriveled fibrotic amniotic strands. This event is probably sporadic, with negligible risk of recurrence. Formation of constrictive tissue bands is associated with abdominal trauma, amniocentesis, and hereditary defects of collagen such as Ehlers-Danlos syndrome and osteogenesis imperfecta.

Adhesive bands involve the craniofacial area and are associated with severe defects such as encephalocele and facial clefts. Adhesive bands result from broad fusion between disrupted fetal parts and an intact amniotic membrane. The craniofacial defects appear not to be caused by constrictive amniotic bands but to result from a vascular disruption sequence with or without cephaloamniotic adhesion (Chapter 102).

The limb–body wall complex (LBWC) involves vascular disruption early in development, affecting several embryonic structures; it includes at least 2 of the following 3 characteristics: exencephaly or encephalocele with facial clefts, thoracoschisis and/or abdominoschisis, and limb defects.

Preauricular Sinuses and Pits

Pits and sinus tracts anterior to the pinna may be a result of imperfect fusion of the tubercles of the 1st and 2nd branchial arches. These anomalies may be unilateral or bilateral, may be familial, are more common among females and blacks, and at times are associated with other anomalies of the ears and face. Preauricular pits are present in branchio-otorenal dysplasia 1 syndrome (EYA-1 gene), an autosomal dominant disorder that consists of external ear malformations, branchial fistulas, hearing loss, and renal anomalies. When the tracts become chronically infected, retention cysts may form and drain intermittently; such lesions may require excision.

Accessory Tragi

An accessory tragus typically appears as a single pedunculated, flesh-colored papule in the preauricular region anterior to the tragus. Less commonly, accessory tragi are multiple or bilateral, and may be located in the preauricular area, on the cheek along the line of the mandible (Fig. 640-1), or on the lateral aspect of the neck anterior to the sternocleidomastoid muscle. In contrast to the rest of the pinna, which develops from the 2nd branchial arch, the tragus and accessory tragi derive from the 1st branchial arch. Accessory tragi may occur as isolated defects or in chromosomal 1st branchial arch syndromes that include anomalies of the ears and face, such as cleft lip, cleft palate, and mandibular hypoplasia. An accessory tragus is consistently found in oculo-auriculo-vertebral syndrome