Protracted febrile myalgia as a challenging manifestation of familial Mediterranean fever: case-based review.

Protracted febrile myalgia syndrome (PFMS) in familial Mediterranean fever (FMF) patients is a vasculitic condition characterized by severe myalgia, fever, abdominal pain, diarrhea, and arthralgia/arthritis episodes lasting 4-6 weeks. Symptoms typically resolve with corticosteroid treatment. However, in recent years, corticosteroid-resistant PFMS patients have been reported. We herein report five pediatric FMF patients complicated with PFMS. In addition, demographic findings, Mediterranean fever (MEFV) gene analysis, symptoms at disease onset, time interval between the diagnoses of FMF and PFMS, co-existent diseases, and treatment responses were evaluated. Resolution of all PFMS symptoms was accepted as complete response, while decreased symptoms without full recovery as partial response. We searched PubMed using the keywords 'protracted febrile myalgia' and 'anakinra', and reviewed the literature. There were three male and two female patients. Median age at the diagnosis of FMF was 6 (3-10) years. The time from diagnosis of FMF to the development of PFMS was changed from 0 to 8 (median: 2) years. All of the patients, except one, had homozygous M694V mutation. All patients were treated with corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs) first. Two out of five patients were exhibited partial response, while others exhibited complete response. Patients with partial response to the conventional therapies were treated with anakinra, and achieved a great response after the first dose. Anti-interleukin-1 (IL-1) therapy may be a beneficial and a reasonable treatment option, when there is insufficient response to NSAID and corticosteroid therapies in pediatric PFMS patients.