Nummular dermatitis consists of well-demarcated, coin-shaped lesions of eczema, typically on the extremities and less often the trunk (Fig. 33-33). Nummular dermatitis tends to worsen in dry, cold weather. Lesions may be mildly to severely pruritic and as a result become excoriated or even lichenified with scratching. Nummular dermatitis can be confused with plaques of psoriasis or tinea corporis but skin scrapings will not reveal hyphae on KOH preparation. Also, lesions lack the typical central sparing of tinea corporis. If necessary, a biopsy can help differentiate nummular eczema from psoriasis.
As with all eczematous dermatitis, general dry skin care is recommended with mild cleansers and bland emollients.
An intermediate to potent topical steroid may be applied two to four times daily to the affected areas. Once lesions improve, a lower-potency steroid should be used to minimize skin atrophy. Pruritus may be treated with an antihistamine if needed.
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