Drug-induced purpura simplex: clinical and histological characteristics

Purpura simplex (PS) is a chronic condition manifesting as purpura, dermatitis and pigmentation. Histologically it is characterised by extravasation of erythrocytes and perivascular inflammation without fibrinoid necrosis. Most cases of PS are idiopathic. In order to determine if PS can be drug induced, a prospective study of 183 patients with PS was carried out. Of these, 27 patients were confirmed to be drug induced, as the purpura cleared on withdrawal of medications within four months. Lesions of drug-induced PS were significantly more generalised as compared to PS patients without a drug history. No epidermal involvement and an absence of lichenoid infiltrate characterised drug-induced as compared to idiopathic PS. NSAIDs, diuretics, meprobamate and ampicillin were the commonest offenders. We conclude that a drug-induced subgroup of PS exists and can be identified by clinical and histological features. Therefore, a careful drug history and skin biopsy are recommended in all cases of PS.