Comprehensive Dermatology Quiz: Diagnosing and Managing Urticaria and Related Skin Conditions

Acute urticaria occurs when an allergen activates mast cells in the skin, and is commonly caused by oral and parenteral drugs, food, and, less frequently, infections. Topical agents and physical abuse are unlikely to present in this manner, and hereditary angioedema is more a systemic illness than a skin disorder.

Although the consequences of nasal (or facial) staphylococcal lesions demand that they receive careful evaluation and culture, most lesions in this area of the face are related to HSV-1 infections. The painful grouped vesicles on an erythematous base indicate a viral infection, likely HSV-1. Herpes zoster would be unlikely because the lesion involves only the distal nose area without other lesions, and symptoms would be unlikely. The appearance of staphylococcal infection would be quite different.

Continuous therapy with oral terbinafine for 12 weeks has the highest cure rate and best long-term resolution rate of the therapies listed. Other agents and pulsed dosing regimens have lower cure rates. Topical creams are not appropriate for onychomycosis because the infection resides in the cell of the toenail. Antifungal nail lacquers have a lower cure rate than systemic therapy and should be used only when oral agents would not be safe.

Xerosis is a pathologic dryness of the skin that is especially prominent in the elderly. It is probably caused by minor abnormalities in maturation of the epidermis that lead to decreased hydration of the superficial portion of the stratum corneum. Xerosis often intensifies in winter, because of the lower humidity and cold temperatures. Stasis dermatitis, due to chronic venous insufficiency, appears as a reddish-brown discoloration of the lower leg. Lichen simplex chronicus, the end result of habitual scratching or rubbing, usually presents as isolated hyperpigmented, edematous lesions, which become scaly and thickened in the center. Rosacea is most often seen on the face as an erythematous, acneiform eruption, which flushes easily and is surrounded by telangiectasia.

Keratoacanthoma grows rapidly and may heal within 6 months to a year. Squamous cell carcinoma may appear grossly and histologically similar to keratoacanthoma but does not heal spontaneously. The other lesions do not resemble keratoacanthoma.

The mite burrow confirms the diagnosis of scabies, but can be missed if the skin is excoriated. Scabies spreads by direct skin contact, and is seldom spread by transfer from bedding. Children frequently have scabies lesions on the face or neck, while this rarely happens in adults. Scabies infections usually cause itching among several family members, but they may not admit it.

Surgical reexcision is the preferred method of treatment for residual basal cell carcinomas, especially around the face. Imiquimod is not recommended for treating lesions on the head or face. Cryotherapy and curettage with electrodesiccation are recommended as primary treatments, but would not be appropriate in this case because lesions on the central part of the face are at risk for extensive subclinicalspread.

Tretinoin, adapalene, and tazarotene are all retinoids and are primarily comedolytic and anti-comedogenic agents. Salicylic acid has a keratolytic effect and can be useful as a peeling agent. Benzoyl peroxide is an antibacterial and is therefore most useful in treating inflammatory papules and pustules.

This patient has typical erythema nodosum, likely related to oral contraceptive use. Careful evaluation of the skin lesions would exclude early rheumatoid arthritis, shin splints, and superficial thrombophlebitis. Papular urticaria, a hypersensitivity reaction to common insect bites such as fleas, mosquitoes, bedbugs and other insects, is another possibility to consider, although these lesions are generally smaller, and papular or papulovesicular in appearance.

Candida causes 95% of cases of chronic paronychia, while the other organisms are more likely to cause acute paronychia.

Herpetic whitlow results from inoculation of type 1 or type 2 herpes simplex virus into broken skin. Health care workers exposed to oral secretions may be susceptible. An abrupt onset of redness and significant localized pain associated with the development of small, clear vesicles is typical. The vesicles often coalesce over the next several days, and the fluid may become cloudy. Fever with epitrochlear and axillary lymphadenopathy also may occur. Herpetic whitlow may mimic other hand infections and injuries, but the history and examination usually lead to an accurate diagnosis, which may be confirmed by viral culture.