29 Skin Problems

Skin problems are one of the most common reasons why patients seek medical attention. The 10 most common skin problems leading patients to consult dermatologists are acne, fungal infections, seborrheic dermatitis, atopic or eczematous dermatitis, warts, benign and malignant skin tumors, psoriasis, hair disorders, vitiligo, and herpes simplex.

Occupational dermatoses (Table 29-1) most often appear as eczematous contact dermatitis, although they occasionally manifest as skin cancers, vitiligo, or infectious lesions. Irritant contact dermatoses are often caused by frequent hand washing, cleansers, solvents, cutting oils used by machinists, and disinfectants. Allergic contact dermatitis is usually caused by frequent exposure to nickel chromates and epoxy resins. Other common lesions are infestations such as scabies and pediculosis, contact dermatitis (Table 29-2), pityriasis rosea, herpes zoster, and seborrheic keratoses.

TABLE 29-1 Potential Allergens in Contact Dermatitis from Occupational Exposure

TABLE 29-2 Common Areas of Involvement and Causes of Allergic Contact Dermatitis

These are not necessarily the most common skin problems; some of the most prevalent are handled by physicians other than dermatologists. About one third of all patients with a primary dermatologic complaint consult a general physician.

This chapter presents the most common dermatologic problems in the table “Differential Diagnosis of Skin Problems” (on page 378). Dermatologic diagnosis is based on the type of lesion, its configuration, and the distribution of the lesions, so the summary table is organized accordingly. See the color insert for illustrations of selected skin conditions. The color photos also portray some common pediatric viral exanthems.

Systemic disease may manifest as skin problems. General pruritus may be caused by anemia, uremia, or liver disease. Erythema nodosum (tender red nodules on the shins) may be associated with sarcoidosis, inflammatory bowel disease, or leukemia. Cutaneous vasculitis may be present in connective tissue disorders such as systemic lupus erythematous or, in an acutely unwell patient, meningococcal meningitis. Café-au-lait spots in children may indicate neurofibromatosis.

Skin tumors are most common later in life. The most common malignant lesions are basal cell epithelioma and squamous epithelioma. Basal cell carcinoma is typically described as a pearl-white, dome-shaped papule with raised edges and overlying telangiectasia. Squamous cell carcinoma is described as having a red, poorly defined base and an adherent yellow-white cutaneous horn. Sqamous cell carcinomas progress into nodular lesions with necrotic centers and are often found within a background of sun-damaged skin and actinic keratoses. Melanomas vary in appearance; 30% develop within existing nevi, and 70% appear de novo. Clinical signs that increase the likelihood that a pigmented lesion is melanoma follow the ABCD mnemonic; Asymmetry, Border irregularity, Color variegation, and Diameter > 6 mm. With proper training, office dermoscopy can be used to differentiate between benign and malignant pigmented skin lesions. If any uncertainty exists about whether a skin lesion is malignant, it should be biopsied. A full-thickness biopsy (as opposed to a shave biopsy) should be performed for any lesion suspicious for melanoma because depth of penetration determines prognosis and treatment.

Differential Diagnosis of Skin Problems

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