Hand-foot-mouth disease. This common and benign viral disease of childhood is usually caused by the A16 strain of coxsackievirus, although other strains of the same virus have been implicated. It most often occurs in late summer and early fall. The prodrome consists of low-grade fever and malaise. Shortly thereafter, vesicular lesions arise on the soft palate, tongue, buccal mucosa, and uvula. The lips are usually spared. Occasionally, these lesions may be painful and cause some difficulty in eating. The cutaneous lesions develop 1 or 2 days after those in the mouth. They consist of asymptomatic round or oval vesiculopustules that evolve into superficial erosions. The edges of the palms and soles are a favored location.
Phototoxic dermatitides. In phototoxic reactivity, no immunologic mechanism is involved, and the patient reacts as anyone would to a primary irritant. Phototoxic drugs and chemicals include some dyes, coal tar derivatives, and psoralens. Drugs that may cause a phototoxic reaction include the sulfonamides, tetracyclines, and thiazides.
Nevus depigmentosus (achromicus). These are localized areas of hypopigmentation that are usually present at birth. The lesions may be irregular in size and shape and occasionally follow a linear or segmental pattern. Electron microscopic study of these areas suggests that melanosomes are not being transferred from melanocytes into surrounding keratinocytes. There are no associated abnormalities.