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. CONCLUSION: 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.