Nummular (discoid) dermatitis is inflammation of the skin characterized by coin-shaped or disc-shaped lesions. Diagnosis is clinical. Treatment may include antibiotics, corticosteroids, and ultraviolet light therapy.

Nummular dermatitis is most common among middle-aged and older patients and is often associated with dry skin, especially during the winter. Id reactions may manifest as nummular dermatitis. The cause is unknown.

Symptoms and Signs

Discoid lesions often start as patches of confluent vesicles and papules that later ooze serum and form crusts. Lesions are pruritic. They can number from 1 to about 50 and tend to be from 2 to 10 cm in diameter. They are often more prominent on the extensor aspects of the extremities and on the buttocks but also appear on the trunk. Exacerbations and remissions may occur, and when they do, new lesions tend to reappear at the sites of healed lesions.

Diagnosis

Diagnosis is clinical based on the characteristic appearance and distribution of the skin lesions. Tests for bacteria and fungi may be done to rule out infection.

Treatment

• Supportive care
• Antibiotics
• Corticosteroids (most often topical, but sometimes intralesional or oral)
• Ultraviolet light therapy

No treatment is uniformly effective. Oral antibiotics (eg, dicloxacillin or cephalexin 250 mg qid) may be given, along with use of tap water compresses, especially when weeping and pus are present. Less inflamed lesions may respond to tetracycline 250 mg po qid, which has a beneficial (although not necessarily antibacterial) effect. Corticosteroid cream or ointment should be rubbed in 3 times daily. An occlusive dressing with a corticosteroid cream under polyethylene film or with flurandrenolide-impregnated tape can be applied at bedtime. Intralesional corticosteroid injections may be beneficial for the few lesions that do not respond to therapy. In more widespread, resistant, and recurrent cases, ultraviolet B radiation alone or oral psoralen plus ultraviolet A (PUVA) radiation may be helpful. Occasionally, oral corticosteroids are required, but long-term use should be avoided; a reasonable starting dose is prednisone 40 mg every other day.

Last full review/revision October 2012 by Karen McKoy, MD, MPH