Schnitzler's syndrome versus adult onset Still's disease

We report the case of a 50-year-old man with a 4-year history of high spiking fever accompanied by a widespread, urticarial, non-pruritic or only sometimes mildly pruritic eruption and arthralgia. He also had generalized lymphadenopathy, hepatosplenomegaly, and hyperosteoses of the lower lumbar spine. Laboratory examination revealed an elevated erythrocyte sedimentation rate, elevated white blood cell and platelet counts, hypoalbuminemia, and elevated serum IgM with IgM kappa monoclonal immunoglobulin. We diagnosed his condition as Schnitzler's syndrome, in contrast to the diagnosis of adult onset Still's disease, for which he had been initially followed up by his internist. We compare clinical and histopathological findings for both diseases and, as this patient meets two of the six existing diagnostic criteria for adult onset Still's disease, we propose that Schnitzler's syndrome is an important entity to be added to the list of differential diagnoses for adult onset Still's disease.