The evolution of histopathologic findings in adult Still disease.

Adult Still disease is an inflammatory arthritis classically associated with daily spiking fevers, evanescent rash, organomegaly, lymphadenopathy, and laboratory anomalies. The typical cutaneous lesions are thin pink papules in a morbilliform distribution, of short duration. Histologically, these lesions are characterized by a superficial perivascular and interstitial mixed dermatitis with lymphocytes and variable neutrophils. A variant clinical presentation is increasingly recognized, which demonstrates persistent hyperpigmented plaques, often with a rippled or linear appearance. The histologic findings consist of upper epidermal dyskeratotic keratinocytes, increased dermal mucin, and a superficial perivascular infiltrate of lymphocytes and possibly neutrophils or eosinophils. We encountered 2 patients who presented with the characteristic rash of adult Still disease, both of whom progressed to develop the pigmented cutaneous plaques. We propose that this variant clinical and histologic appearance is the outcome of persistent disease activity.