ABSTRACT
The eruption of nummular dermatitis consists of discrete, round, erythematous, edematous, and crusted plaques usually localized on the dorsal aspect of the hands, extensor surfaces of the arms, legs, thighs, and buttocks. Nummular dermatitis lesions ordinarily appear pink or reddish in white people but are often brown, purple, or black in people of colour. Although patients with atopic dermatitis can have typical nummular dermatitis lesions, they will usually have symmetrical flexural eczema, lichenification, or other distinguishing clinical features. Histological changes of nummular dermatitis vary with the stage of the lesions. The differential diagnosis of nummular dermatitis includes atopic dermatitis, allergic contact dermatitis, psoriasis, lichen simplex chronicus, cutaneous drug eruption, mycosis fungoides, pityriasis rosea, impetigo, tinea, and syphilis. Patients with nummular dermatitis should be evaluated for duration and extent of disease, severity of itching, previous treatment, bathing habits, and possible exacerbating factors such as contactants, medications, or occult infection.
