Nummular eczema, also called discoid dermatitis, is an inflammatory dermatitis, which presents as well-demarcated annular xerotic and erythematous plaques on the arms or legs. It derives its name from its characteristic coin-shaped skin lesions.1-3 Initially, nummular eczema can present as oozing papules and/or vesicles. These papules and vesicles later dry and coalesce into round plaques.2
The etiology of nummular eczema differs from that of classic atopic eczema. With atopic eczema and asthma, an intrinsic allergen can be the cause of the hypersensitivity and skin lesions. Rather, nummular eczema is most often the result of a contact allergen.2 Exposure to hot water, soaps and detergents, and cold weather can exacerbate nummular eczema.4
The location of the discoid lesions is important in making a diagnosis of nummular eczema. The dorsal aspects of the hands, extensor surfaces of the forearms, the upper arms, legs, thighs and feet are most often affected.4 Patients may complain of accompanying pruritus with these lesions. The differential diagnosis should include contact dermatitis, tinea corporis, psoriasis, lichen simplex chronicus and Majocchi’s granuloma.
Treatment of nummular eczema begins with topical mid- to high-potency corticosteroids.2 One can treat lesions on the feet with triamcinolone 0.5% cream or ointment with twice daily applications for two weeks.2 Unfortunately, nummular eczema frequently becomes a chronic condition with rash recurrence.
1. Todorova A, Bruckbauer H, Ring J. In Katsambas AD, Lotti TM, Dessinioti C, D’Erme AM (eds.) Nummular eczema. European Handbook of Dermatological Treatments. Springer, Berlin, 2015, pp. 671-680.
2. Reich D, Psomadakis CE, Buka B. Nummular eczema. Top 50 Dermatology Case Studies for Primary Care. Springer International Publishing, Berlin, 2017, pp. 167-172.
3. White J. Non-atopic dermatitis. Medicine. 2017; 45(6):383–5.
4. Halberg M. Nummular eczema. J Emerg Med. 2012; 43(5):e327-e328.