Mixed diagnoses – 10 cases (8 of 11)

This is nummular dermatitis (also known as discoid eczema), an idiopathic skin disorder.

Individual lesions start as pruritic papules or vesicles that become confluent plaques. They may arise on any area of skin, most frequently the lower legs and dorsa of the hands. Characteristically there are coin-shaped erythematous lesions, which may be exudative and crusted or dry and scaly. Frequently, staphylococcus aureus can be cultured; there is debate whether this is a secondary infection or whether it has a primary role in pathogenesis. Nummular dermatitis is frequently confused with other forms of dermatitis, psoriasis, tinea corporis and pityriasis rosea.

Nummular dermatitis can be hard to control but generally improves or remits after several months.

Minimise heat and humidity; the patient should wear cool clothing

Emollients should be applied frequently and liberally, especially after bathing

Potent topical steroids are applied to the plaques once or twice daily for two to four weeks, followed by mild topical steroids. A cream base is most suitable for weeping lesions; an ointment base is more appropriate if the lesions are dry.

Oral antistaphylococcal antibiotics are recommended during the exudative phase, and are sometimes helpful long term (eg dicloxacillin, erythromycin)

Phototherapy or photochemotherapy (PUVA) is helpful for extensive dermatitis

Rarely, systemic steroids and/or other immunosuppressive agents are necessary for severe cases.