A Case of Protracted Febrile Myalgia Syndrome with Atypical Course and Severe Asymmetric Loss of Muscle Strength.

Protracted febrile myalgia syndrome (PFMS) is a rare form of familial Mediterranean fever (FMF) characterised by prolonged myalgia. The duration of PFMS is much longer than a typical 2-5-day attack familial Mediterranean fever and lasts for 2-6 weeks until they treated with corticosteroids. Colchicine is not effective for control of PFMS's attacks. The attacks typically resolve with corticosteroid and/or IL-1 receptor blockers. Herein, we present a young adult without typical familial Mediterranean fever clinical features but presenting with atypical course and severe asymmetric muscle strength loss. Thigh magnetic resonance imaging confirmed inflammation and oedema and muscle biopsy showed no pathological findings. Electromyography revealed myopathic findings during attack-period, despite normal results in attack-free study. The patient was treated successfully with anakinra and remarkable rapid recovery in both muscular findings and acute phase reactants were observed. PFMS should be considered even in the absence of apparent FMF attack pattern and in the presence of unexpected severe muscle weakness, especially in areas endemic for FMF and long-lasting myalgia attacks.