Protracted febrile myalgia in children and young adults with familial Mediterranean fever: Analysis of 15 patients and suggested criteria for working diagnosis

Objectives. To present an analysis of patients with protracted febrile myalgia (PFM), a rarely reported manifestation of familial Mediterranean fever (FMF), and propose clinical criteria for working diagnosis. Methods. A multicenter retrospective cohort study of children with PFM was performed. Clinical and laboratory data were obtained by medical record review. Results. The study group included 15 patients with PFM. PFM occurred as the presenting sign of FMF in 33%. FMF was diagnosed clinically in all and by genetic analysis in 93%. M694V allelic involvement was noted in 93% of the patients. PFM occurred at a mean age of 9 ± 3.4 years and was characterized by severe generalized muscle pain in all patients and fever in 71%. Mean duration up to diagnosis was 15.5 ± 6 days. Mean erythrocyte sedimentation rate was 104 ± 26 mm/h; mean C-reactive protein was 15.4 ± 6.3 mg%. Creatine kinase was normal. Treatment included corticosteroids (4 patients) and nonsteroidal anti-inflammatory drugs (NSAIDs) (9 patients) with a symptomatic relief achieved at a mean of 7. 7 ± 4.3 days and 5 ± 3.8 days, respectively (p = 0.14) (mean severity score 3 and 2.2, respectively, p = 0.075). Symptomatic relief in 2 untreated patients was achieved at a mean of 45.5 days. Conclusions. Based on our data, we propose criteria for working diagnosis including: severe disabling myalgia of at least 5 days in a young patient with FMF, associated with fever, elevated levels of inflammatory markers and presence of at least one M694V mutation.