Background Protracted febrile myalgia (PFM) is a rare and least well recognized manifestation of familial Mediterranen fever (FMF), characterized by prolonged excruciating muscle pain, tenderness, fever, and elevated levels of acute phase reactants. While the diagnosis of PFM in the setting of previously diagnosed FMF is mostly clinical, diagnosis of PFM when it is the sole manifestation of FMF might be challenging. Objectives To analyse clinical, laboratory, genetic, electrophysiologic, histopathologic, and magnetic resonance imaging (MRI) findings in a series of patients who presented to our department with myalgia and diagnosed as having PFM secondary to FMF. Methods We describe a retrospective cohort PFM patients seen at our department between 2009 and 2012. Clinical, laboratory, and imaging data were obtained by medical record review. Results Study group consisted of 20 (19 male, mean age = 20 years, SD = 3.2) patients. Four (20%) of the patients had a previous diagnosis of FMF, while PFM occurred as the presenting symptom of FMF in 40%. Mean age of disease onset was 17 ± 2.6 years, characterized by severe muscle pain in lower extremities in all patients and affecting single extremity in 90% of the cases. M694V allelic involvement was noted in 80% of the patients. Muscle enzymes were in normal range in all patients, and EMGs were normal in all studied patients (n=13), but one. None of the patients in whom muscle biopsy was available (n=8) showed features compatible with myositis. All of the patients underwent MRI of the symptomatic extremity and showed different degrees of involvement on the MR images of the affected extremities. On MR images, the muscle involvement was either patchy or diffuse, displayed with the high signal intensity on fluid sensitive and gadolinium-enhanced fat saturated T1-weighted images. Extension of the inflammation around individual muscles and muscle groups (myofascial distribution) was observed, as well as subcutaneous tissue edema. Conclusions This series of patients with PFM, to our knowledge, is the largest one reported in the literature. PFM can be the initial manifestation of FMF in some of the patients. Due to the lack of any specific abnormalities other than elevated acute phase response, diagnosis of such cases possess some difficulties. With the appropriate clinical history, detection of MRI findings compatible with myositis in the absence of other features suggestive of myositis (muscle enzymes, EMG, etc.) can help make or confirm the diagnosis of PFM, particularly in areas where the FMF is prevalent. Disclosure of Interest None Declared