Skina and Hair Disorders

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Seborrhoeic warts, keratoacanthomas and cutaneous horns are benign epidermal proliferations characterized by excess keratin production.
Seborrhoeic keratoses are extremely common, increasing in number with age. They are almost invariably multiple and present as slightly raised, greyish brown keratotic lesions, the larger examples of which may have an obviously warty surface. They are due to proliferation of epidermal cells resembling those that occupy the basal layer, and there is excessive production of keratin. They are invariably benign.

Keratoacanthoma most commonly occurs in the elderly, particularly on the face. A characteristic and frightening feature is that they clinically resemble squamous-cell carcinomas and grow extremely rapidly, changing in a matter of weeks from a slightly raised, red papule to a large domed nodule with raised, firm edges and a central mass of keratin. At certain stages in their growth, keratoacanthomas also share histological features with squamous-cell carcinoma, and the differential diagnosis can be very difficult. Most keratoacanthomas spontaneously regress within some months, but those that persist should be excised because of the difficulty of distinguishing them from squamous-cell carcinomas.
Cutaneous horns are hard, protruding lumps of keratin that arise from an area of abnormal epidermis. The underlying epidermal abnormality is usually benign, e.g. a viral wart or seborrhoeic keratosis, but occasionally cutaneous horns can arise on an area of intraepidermal carcinoma.

These are often covered by a thick layer of warty, grey keratin.
Typical lesion with a raised, red edge. It is filled with creamy grey masses of keratin. These can be clinically mistaken for squamous-cell carcinoma of the skin.

Disorders of the hair and hair follicles are very commonly encountered in community practice

Hair follicles are the site of both keratin retention and bacterial and fungal infection (superficial folliculitis). Acute superficial folliculitis is usually due to Staphylococcus aureus. It is most common in the beard area in adolescent and young adult males, but may also occur elsewhere, e.g. the thighs and buttocks. Clinically it presents as minute, yellowish, rounded pustules, often with a central hair. Deep folliculitis occurs when the infection (also usually staphylococcal) occurs deep in the hair follicle. This causes an expanding mass that destroys the follicle, producing a 'boil'.

Acne vulgaris, which most commonly affects adolescents, is a form of chronic folliculitis associated with excess keratin accumulation in the pilosebaceous duct. The infective lesion probably arises in obstructed hair follicles, which produce small, raised, white nodules (whiteheads or blackheads). Rupture of these nodules releases a mixture of keratin, sebaceous-gland secretion and bacteria into the surrounding dermis, where there is a mixed inflammatory reaction, both acute inflammatory and chronic granulomatous. Sometimes acne forms large tender keratin-filled cysts (cystic acne). The cause is not known, but high circulating androgens are thought to be significant.
Rosacea, is a follicle-related disease in which there is marked reddening of the skin of the face, associated with telangiectatic dilatation of upper dermal vessels and a perivascular chronic inflammatory infiltrate which, when heavy, leads to persistent indurated reddening of the skin. Papules or pustules frequently develop, and are based on markedly dilated hair follicles in which fragments, live or dead, of the mite Demodex folliculorum are commonly found. The most floridly lumpy forms of rosacea are those that occur when the follicles rupture, their contents exciting a giant-cell granulomatous reaction (granulomatous rosacea), or when the lesion occurs in an area of marked sebaceous gland hyperplasia, commonly the noses of elderly men {\B (rhinophyma).}

Abnormal hair loss is called alopecia and there are many types

Hair loss from the scalp is a normal ageing change, with exaggerated or early loss in those in whom there is a family predisposition (particularly men). There are many causes of hair loss outside the normal range, the most common being alopecia areata. Other types of alopecia include alopecia totalis and universalis (loss of all head hair and all body hair, respectively), trichotillomania (traumatic hair loss due to avulsion, usually self-inflicted, of the hair from the follicle for aesthetic or psychological reasons), and scarring alopecia (usually the result of inflammatory destruction of hair follicles due to some other disease, e.g. lupus erythematosus or lichen planus, affecting the hair follicles.

Alopecia areata is the most common type of pathological hair loss

In alopecia areata there is sudden onset of round or oval patches of baldness in the scalp, leaving unusually smooth, almost shiny skin. The patches persist for many months, but in most cases the hair grows back within 12-18 months, although further patches may develop. A few progress to alopecia totalis. 
The disease is multifactorial, and there is often a family history; more than half of the patients have a history of atopic eczema, asthma, or an autoimmune disease (particularly of the thyroid). It is common in association with Down's syndrome. 
There appears to be a sudden loss of anagen (growing) hairs, and the follicles enter the resting catagen/telogen phase, during which time there is a perifollicular infiltrate by lymphocytes.

The most common ulcers of the skin occur on the lower legs and are associated with chronic venous insufficiency

Most common in middle-aged and elderly women with varicose veins, chronic venous insufficiency in the lower legs and gravitational dermatitis, 'varicose' or 'venous' ulcers are a common and persistent problem in community practice. They are shallow but often spreading ulcers, forming on a background of chronic gravitational dermatitis and pigmentation in the fragile atrophic skin around the ankles and lower shin . They show little tendency to heal spontaneously, and secondary infection is common; some of the topical applications used to treat or prevent bacterial infection produce a contact dermatitis, leading to deterioration of the ulcer. 
Occasionally, chronic skin ulcers have a slightly raised purplish edge; these ulcers may be the result of vasculitic lesions in dermal vessels.
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Revised: 02-11-2014.