Etiology/Pathogenesis

Hyperhidrosis is excessive sweating beyond what is physiologically necessary for temperature control and occurs in 3% of the population with about half having axillary hyperhidrosis. The numerous disorders that may be associated with increased production of eccrine sweat may also be classified into those with neural mechanisms involving an abnormality in the pathway from the neural regulatory centers to the sweat gland and those that are non-neurally mediated and occur by direct effects on the sweat glands (Table 653-1).

Clinical manifestations

The average age at onset of hyperhidrosis is 14-25 yr. The excess sweating may be continuous or may occur in response to emotional stimuli. In severe cases, sweat may be seen to drip constantly from the hands.

Treatment

Excessive sweating of the palms and soles (volar hyperhidrosis) and axillary sweating may respond to 20% aluminum chloride in anhydrous ethanol applied under occlusion for several hours, iontophoresis (palms and soles only), injection with botulinum toxin, therapy with oral anticholinergics, or in severe, refractory cases, cervicothoracic or lumbar sympathectomy.

Etiology/Pathogenesis

Miliaria results from retention of sweat in occluded eccrine sweat ducts. The keratinous plug does not form until the later stages of the disease, and therefore, does not appear to be the primary cause of the sweat duct obstruction. The initial obstruction is postulated to be due to swelling of the ductal epidermal cells, perhaps from imbibition of water. Retrograde pressure may result in rupture of the duct and leakage of sweat into the epidermis and/or the dermis. The eruption is most often induced by hot, humid weather, but it may also be caused by high fever. Infants who are dressed too warmly may demonstrate this eruption indoors, even during the winter.

Clinical Manifestations

In miliaria crystallina, asymptomatic, noninflammatory, pinpoint, clear vesicles may suddenly erupt in profusion over large areas of the body surface, leaving brawny desquamation on healing (Fig. 653-1). This type of miliaria occurs most frequently in newborn infants because of the relative immaturity and delayed patency of the sweat duct and the tendency for infants to be nursed in relatively warm, humid conditions. It may also occur in older patients with hyperpyrexia.

Figure 653-1 Superficial clear vesicles of miliaria crystallina.

Miliaria rubra is a less superficial eruption characterized by erythematous, minute papulovesicles that may impart a prickling sensation. The lesions are usually localized to sites of occlusion or to flexural areas, such as the neck, groin, and axillae, where friction may have a role in their pathogenesis. Involved skin may become macerated and eroded. Lesions of miliaria rubra, however, are extrafollicular.

Repeated attacks of miliaria rubra may lead to miliaria profunda, which is due to rupture of the sweat duct deeper in the skin, at the level of the dermal-epidermal junction. Severe, extensive miliaria rubra or miliaria profunda may result in disturbance of heat regulation. Lesions of miliaria rubra may become infected, particularly in malnourished or debilitated infants, leading to development of periporitis staphylogenes, which involves extension of the process from the sweat duct into the sweat gland.

Histology

Histologically, miliaria crystallina reveals an intracorneal or subcorneal vesicle in communication with the sweat duct, whereas in miliaria rubra, one sees focal areas of spongiosis and spongiotic vesicle formation in close proximity to sweat ducts that generally contain a keratinous plug.

Differential Diagnosis

The clarity of the fluid, superficiality of the vesicles, and absence of inflammation permit differentiation of miliaria crystalline from other blistering disorders. Miliaria rubra may be confused with or superimposed on other diaper area eruptions, including candidosis and folliculitis.

Treatment

All forms of miliaria respond dramatically to cooling of the patient by regulation of environmental temperatures and by removal of excessive clothing; administration of antipyretics is also beneficial to patients with fever. Topical agents are usually ineffective and may exacerbate the eruption.

Etiology/Pathogenesis

Hidradenitis suppurativa is a disease of the apocrine gland–bearing areas of the skin. Pathogenesis of hidradenitis suppurativa is controversial. It is now believed that it is a primary inflammatory disorder of the hair follicle and not solely an alteration of apocrine glands. It is considered a part of the follicular occlusion tetrad, along with acne conglobata, dissecting cellulites of the scalp, and pilonidal sinus. Bacterial infection, particularly with Staphylococcus aureus, Streptococcus milleri, Escherichia coli, and, possibly, anaerobic streptococci, appears to be important in the progressive dilatation below the obstruction, leading to rupture of the duct, inflammation, sinus tract formation, and destructive scarring.

Clinical Manifestations

Hidradenitis suppurativa is a chronic, inflammatory, suppurative disorder of the apocrine glands in the axillae, the anogenital area, and, occasionally, the scalp, posterior aspect of the ears, female breasts, and periumbilical area. Onset of clinical manifestations is sometimes preceded by pruritus or discomfort and usually occurs during puberty or early adulthood. Solitary or multiple painful erythematous nodules, deep abscesses, and contracted scars are sharply confined to areas of skin containing apocrine glands. When the disease is severe and chronic, sinus tracts, ulcers, and thick, linear fibrotic bands develop. Hidradenitis suppurativa tends to persist for many years, punctuated by relapses and partial remissions. Complications include cellulitis, ulceration, and burrowing abscesses that may perforate adjacent structures, forming fistulas to the urethra, bladder, rectum, or peritoneum. Episodic inflammatory arthritis develops in some patients.

Histology

Early lesions are characterized by a keratinous plug in the apocrine duct or hair follicle orifice and by cystic distention of the follicle. The process generally but not necessarily extends into the apocrine gland. Later changes include inflammation within and around apocrine glands and the presence of groups of cocci within apocrine glands and in the adjacent dermis. Scarring may obliterate skin appendages.

Differential Diagnosis

Early lesions of hidradenitis suppurativa are often mistaken for infected epidermal cysts, furuncles, scrofuloderma, actinomycosis, cat-scratch disease, granuloma inguinale, or lymphogranuloma venereum. Sharp localization to areas of the body that bear apocrine glands, however, should suggest hidradenitis. When involvement is limited to the anogenital region, the condition may be difficult to distinguish from Crohn disease.

Treatment

Conservative management includes cessation of smoking, weight loss, and avoidance of irritation of the affected area. Warm compresses and topical antiseptic or antibacterial soaps may also be helpful. For mild, early, disease, topical clindamycin 1% is the treatment of choice. For more severe disease therapy may be initiated with tetracycline (500 mg bid), doxycycline (100 mg bid), or minocycline (100 mg bid). Some patients require intermittent or long-term antibiotic treatment. Oral retinoids (1 mg/kg/day) for 5-6 mo may also be effective. Oral contraceptive agents, which contain a high estrogen : progesterone ratio and low androgenicity of the progesterone, are another alternative. Surgical measures may be required for control or cure.

Etiology/Pathogenesis

The cause of Fox-Fordyce disease is unknown.

Clinical Manifestations

This disease is most common in females and manifests during puberty to the 3rd decade of life as pruritus in the axillae. Pruritus is exacerbated by emotional stress and stimuli that induce apocrine sweating. Dome-shaped, skin-colored to slightly hyperpigmented, follicular papules develop in the pruritic areas.

Histology

Histopathologically, one sees keratinous plugging of the distal apocrine duct, rupture of the intraepidermal portion of the apocrine duct, paraductal microvesicle formation, and paraductal acanthosis.

Treatment

Fox-Fordyce disease is difficult to treat. Oral contraceptive pills and topical corticosteroids or retinoic acid may help some patients.