Adult-onset Still's disease: how to make a diagnosis in an atypical case.

Adult-onset Still's disease (AOSD) is a complicated multi-systemic inflammatory disease, the main features of which are high spiking fever, evanescent rash, polyarthralgia, lymphadenopathy, hepatosplenomegaly and leukocytosis. The pathogenesis and etiology of AOSD are still unknown. We report a case of atypical AOSD presenting with only arthralgia, fever, lymphadenopathy, slightly elevated serum C-reactive protein and ferritin levels and a slightly elevated erythrocyte sedimentation rate; these signs and symptoms did not fulfill the proposed diagnostic criteria of both Cush and Yamaguchi. After exclusion of other likely diagnoses, a diagnosis of atypical AOSD was made, and a low dose of corticosteroids was effective in resolving all of the patient's symptoms. More clinical practice and research are needed to determine pathogenesis and etiology of AOSD and to amend the diagnostic criteria to include such atypical cases.