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Common Skin Diseases

I. Alopecia Areata

• A. Alopecia areata is characterized by asymptomatic, noninflammatory, non-scarring areas of complete hair loss, most commonly involving the scalp, but the disorder may involve any area of hair-bearing skin.
• B. It is probably caused by auto-antibodies to hair follicles. Emotional stress is sometimes a precipitating factor. The younger the patient and the more widespread the disease, and the poorer the prognosis.
• C. Regrowth of hair after the first attack takes place in 6 months in 30% of cases, with 50% regrowing within 1 year, and 80% regrowing within 5 years. Ten to 30% of patients will not regrow hair; 5% progress to total hair areta
• D. Lesions are well defined, single or multiple, round or oval areas of total hair loss. In active lesions, "exclamation point" hairs (loose hairs 3-10 mm in size with a tapered, less pigmented proximal shaft) are seen at the margins.
• E. Differential Diagnosis: Tinea capitis, trichotillomania, secondary syphilis, and lupus erythematosus.
• F. A VDRL or RPR test for syphilis should always be obtained. A CBC, SMAC, sedimentary rate, thyroid function tests, antinuclear antibody should be done to screen for pernicious anemia, chronic active hepatitis, thyroid disease, lupus erythematosus, and Addison's disease.
• G. Therapy. Topical steroids, intralesional steroids, and topical minoxidil may be somewhat effective. Hair regrowth will usually occur in 1 year without 

Linear Nevus Syndrome
This sporadic condition is characterized by a facial nevus and neurodevelopmental abnormalities. The nevus is located on the forehead and nose, and tends to be midline in its distribution. It may be quite faint during infancy but later becomes hyperkeratotic with a yellow-brown appearance. More than one half of the patients have a seizure disorder and are mentally retarded. The seizures may be generalized myoclonic or focal motor. Most patients have normal CT studies, although hemimegalencephaly with hamartomatous changes has been reported. Focal neurologic signs including hemiparesis and homonymous hemianopia are more common in this group.

II. Scabies

• A. Scabies is characterized by an extremely pruritic eruption usually accentuated in the groin, axillae, navel, breasts, and finger webs, with sparing the head.
• B. Scabies is spread by skin to skin contact. The diagnosis is established by finding the mite, ova, or feces in scrapings of the skin, usually of the finger webs or genitalia.
• C. Treatment of choice for nonpregnant adults and children is gamma benzenehexachloride (Kwell), applied for 8-12 hours, then washed off. CNS toxicity has been reported in infants in whom it was used too frequently.
• D. Elimite, a 5% permethrin cream, is skin diseases, rash, alopecia areata, scabies, rosacea more effective but more expensive than lindane (Kwell).
• E. Treatment should be given to all members of an infected household simultaneously. Clothing and sheets must be washed on the skin diseases, rash, alopecia areata, scabies, rosacea, acne, lice day of treatment. Treatment failures usually result from incomplete treatment or failure to treat all members of the household simultaneously.

III. Acne Rosacea

• A. This condition commonly presents in fair-skinned individuals and is characterized by papules, erythema, and telangiectasias.
• B. Initial treatment consists of doxycycline or tetracycline. Once there has been some clearing, topical metronidazole gel (Metro-gel) can prevent remission. Sunblock should be used because sunlight can exacerbate acne rosacea.

IV. Seborrheic Dermatitis

• A. Seborrheic dermatitis is often called cradle cap, dandruff, or seborrhea. It has a high prevalence in infancy, and then is not common until after puberty. Predilection is for the face, retroauricular region, and upper trunk.
• B. Clinical Findings
• 1. Infants present with adherent, waxy, scaly lesions on the scalp vertex also known as "cradle cap."
• 2. In adults, the eruption is bilaterally symmetrical, affecting the scalp with patchy or diffuse, dull, yellow-like erythema, and waxy yellow, greasy scaling on the forehead, retroauricular region, auditory skin diseases, rash, alopecia areata, scabies, rosacea meatus, eyebrows, cheeks, and nasolabial folds.
• 3. Trunk areas affected include the skin diseases, rash, alopecia areata, scabies, rosacea presternal, interscapular regions, the umbilicus, intertriginous surfaces of the axilla, inframammary regions, groin, and anogenital crease.
• 4. Pruritus is mild, and bacterial infection is indicated by vesiculation and oozing.
• C. Treatment
• 1. Scalp: Selenium sulfide or tar shampoos are useful. Sulfur and salicylic acid lotions can be used as keratolytics; topical corticosteroid lotions are used for difficult lesions.
• 2. Face, neck, and intertriginous regions: Hydrocortisone 1 or 2 ½%.
• 3. Trunk: Fluorinated steroids can be used if severe lesions are present.

V. Drug Eruptions

• A. Drug eruptions may be type I, type II, type III, or type IV immunologic reactions.
• B. Cutaneous drug reactions may start within 7 days of initiation of the drug or within 4-7 days after the offending drug has been stopped.
• C. The cutaneous lesions usually become more severe and widespread over the following several days to 1 week and then clear over the next 7-14 days.