Nummular Dermatitis

It is a chronic recurring rash that seem to occur in the drier, colder months. The lesions are usually round, disk-like plaques or patches of very dry skin. They usually start as small papules (bumps) or vesicles (small blisters) that become eroded and crusted. They are often very itchy and there is sometimes a burning sensation. This condition is often seen in older individuals. Similar looking round patches of dermatitis may be seen in children with atopic dermatitis.

The cause is unknown. Some feel that stress may cause this condition to flare. It often becomes more common in a dry winter climate.

It is most commonly seen on the lower legs, buttocks, forearms and the backs of the hands.

Other conditions that need to be considered when looking at nummular dermatitis are psoriasis, tinea corporis, and parapsoriasis (although this is usually not itchy). Drug eruptions have been reported as presenting with eczema or nummular dermatitis appearance. Other conditions may have superficial similarities including impetigo, Bowen’s disease and mycosis fungoides. In situations where there is doubt, KOH examination or bacterial swabs and / or biopsy may be required.

Patch testing can be useful. In some cases where a contact dermatitis can be identified, clearing can be achieved by avoidance of the allergen.

Treatment:

It is important to reduce contact with irritants. In the acute stage compressing can sometimes have a drying effect on lesions that may be weepy. The mainstay of therapy is the use of mid to high potency topical corticosteroid ointment. Occasionally tar creams or ointments such as 10% LCD in hydrophilic petrolatum can be utilized. Oral antibiotics are sometimes required when there is secondary infection. In very stubborn or severe cases UVB (ultraviolet B) or oral prednisone or cyclosporine have been used.

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