Nummular Eczema: An Updated Review

Background: Nummular eczema may mimic diseases that present with annular configuration and the differential diagnosis is broad. Objective: This article aimed to provide an update on the evaluation, diagnosis, and treatment of nummular eczema. Methods: A PubMed search was performed in using the key terms “nummular eczema”, “discoid eczema”, OR “nummular dermatitis”. The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews. The search was restricted to English literature. The information retrieved from the above search was used in the compilation of the present article. Patents were searched using the key terms “nummular eczema”, “discoid eczema”, OR “nummular dermatitis” in www.google.com/patents and www.freepatentsonline.com. Results: Nummular eczema is characterized by sharply defined, oval or coin-shaped, erythematous, eczematous plaques. Typically, the size of the lesion varies from 1 to 10cm in diameter. The lesions are usually multiple and symmetrically distributed. Sites of predilection include the lower limbs followed by the upper limbs. The lesions are usually intensely pruritic. The diagnosis is mainly clinical based on the characteristic round to oval erythematous plaques in a patient with diffusely dry skin. Nummular eczema should be distinguished from other annular lesions. Dermoscopy can reveal additional features that can be valuable for correct diagnosis. Biopsy or laboratory tests are generally not necessary. However, a potassium hydroxide wet-mount examination of skin scrapings should be performed if tinea corporis is suspected. Because contact allergy is common with nummular eczema, patch testing should be considered in patients with chronic, recalcitrant nummular eczema. Avoidance of precipitating factors, optimal skin care, and high or ultra-high potency topical corticosteroids are the mainstay of therapy. Recent patents related to the management of nummular eczema are also discussed. Conclusion: With proper treatment, nummular eczema can be cleared over a few weeks, although the course can be chronic and characterized by relapses and remissions. Moisturizing of the skin and avoidance of identifiable exacerbating factors, such as hot water baths and harsh soaps may reduce the frequency of recurrence. Diseases that present with annular lesions may mimic nummular eczema and the differential diagnosis is broad. As such, physicians must be familiar with this condition so that an accurate diagnosis can be made, and appropriate treatment initiated.