Protracted febrile myalgia mimicking polyarteritis nodosa.

An insidious onset of unexplained fever, weight loss, skin lesions, abdominal pain, and musculoskeletal pain should suggest the diagnosis of polyarteritis nodosa (PAN). However, familial Mediterranean fever (FMF) with protracted febrile myalgia (PFM) should be kept in mind in the differential diagnosis. In this report, 6 cases of PFM mimicking PAN are described. Patients presented with severe muscle and abdominal pain lasting longer than 4 weeks. Their common medical history included recurrent febrile abdominal pain or arthritis. Physical examination revealed hypertension together with severe muscle tenderness. Laboratory examination revealed high acute phase reactants, negative p-ANCA, normal creatine kinase, and complement levels. Duplex abdominal ultrasonography was normal. Four of 6 patients were hospitalized with initial diagnoses of PAN. Renal and mesenteric angiography performed in 1 patient was normal. Steroid therapy controlled all the severe symptoms including hypertension in all of the cases.FMF with PFM is important in the differential diagnosis of patients with suspected vasculitis especially when myalgia is present. Hypertension may be present as a result of sympathetic discharge because of severe myalgia. Because PFM rapidly responds to a short course of corticosteroids, a rapid diagnosis of PFM in FMF patients can reduce unnecessary workup and decrease the time patients have to suffer.