Persistent plaques and linear pigmentation have been reported as specific skin lesions in some patients with adult-onset Still's disease (AOSD).

We sought to characterize the histologic findings of AOSD-associated persistent rash in 11 cases and correlate the histologic findings with the clinical features.

From 1988 to 2004, 17 cases fulfilling Yamaguchi's criteria for AOSD in our hospital were reviewed and 11 (65%) manifested persistent papules and plaques. The pathology of 13 biopsy specimens of persistent eruption from 9 patients was reviewed.

The 11 patients consisted of 3 men and 8 women with age of onset ranging from 19 to 67 years (average 34.7 years). Evanescent Still's rash was recorded in 9 patients. The persistent rash manifested as pruritic, red, violaceous, or brownish scaly or crusted lichenoid papules and plaques usually widely distributed over the trunk, neck, face, and extensor sides of the extremities. Lesions arranged in a bizarre linear pattern resulting from scratching were noted in some patients. Three patients died of severe disease, systemic complications, or both. The histology of persistent papules and plaques was characterized by: (1) multiple individual necrotic keratinocytes, singly or in aggregates, mainly located in the upper epidermis, including the normal or parakeratotic horny layer; and (2) infiltration of lymphocytes and neutrophils in the papillary and middermis. Other less common findings included basal vacuolar alteration, nuclear dust, and subcorneal or intracorneal pustules.

A clinically and pathologically distinct form of persistent lichenoid eruption was commonly observed in our patients with AOSD. The combination of multiple individual necrotic keratinocytes in the upper epidermis and a dermal infiltrate of neutrophils allow for histologic differentiation of this persistent eruption from most other lichenoid and interface dermatitides and may facilitate an earlier diagnosis of AOSD.