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Coin-shaped eczema
Medical expert of the article
Last reviewed: 07.07.2025
Nummular eczema is a form of eczema characterized by the presence of often generalized, intensely itchy, rounded (coin-shaped) foci of eczematous inflammation. Adults are more often affected, men more often than women.
Symptoms of Nummular Eczema
The onset is gradual, without obvious worsening and without a history of eczema. Nummular eczema often begins with a few isolated lesions on the legs; over time, multiple lesions develop in no specific location. The lesions often resolve or improve with topical corticosteroids, but sometimes return in the same location after discontinuation of corticosteroids.
Well-defined, scaly, circular eczematous plaques appear on the trunk and extremities. Weeping lesions and vesiculation are characteristic of outbreaks. Secondary infection may trigger outbreaks. Honey-yellow crusts indicate secondary impetiginization.
This is one of the most difficult forms of eczema to treat. The course of the disease is variable and unpredictable. The condition can be chronic and recurring over several years. Once formed, lesions tend to maintain their size and recur on previously affected skin.
Diagnosis of nummular eczema
The patch test is positive in 1/3 of cases. Culture may reveal the presence of Staphylococcus aureus. Antibacterial treatment usually helps, but often does not lead to remission.
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Differential diagnosis
Psoriasis (often more symmetrical and "geographical" lesions with silvery scales). Fungal infections (lesions regress centrally and flake at the periphery; KOH examination helps in making a differential diagnosis). Cutaneous T-cell lymphoma of the lower extremities (may be mistaken for nummular eczema; biopsy will help exclude the diagnosis).
Treatment of nummular eczema
All nonessential topical moisturizers, oral medications, dietary supplements, and herbal preparations should be discontinued for at least 3 to 4 months. Athlete's foot should be evaluated; fungal infection, if present, is treated with antifungal agents since generalized nummular eczema may occasionally be an "idc" reaction to a fungal infection. A moderate-strength topical steroid and emollients should be used aggressively. The topical steroid is applied to the affected skin twice daily for 2 to 3 weeks. It is best to continue treatment for a week or longer than necessary for resolution of the lesions. The effectiveness of the topical steroid is enhanced by occlusion with plastic wrap or a sauna suit, by taking a moisturizing bath before applying the topical steroid, or by using both.
Secondary infection is treated with systemic antistaphylococcal antibiotics (eg, cephalexin 250 mg four times daily). Antihistamines are given for pruritus. Systemic steroids are not used for long-term treatment. Phototherapy may result in resolution of lesions if topical therapy is ineffective. Narrow- and broad-spectrum ultraviolet B are the best phototherapy; psoralen plus ultraviolet A may be used if ultraviolet B is ineffective.