Protracted Febrile Myalgia Syndrome: A Rare and Difficult Manifestation of Familial Mediterranean Fever.

Objective: Protracted febrile myalgia syndrome (PFMS) is characterized by severe myalgia, fever, abdominal pain, and arthralgia/arthritis episodes lasting for several weeks in patients with familial Mediterranean fever. Treatment options include nonsteroidal anti-inflammatory drugs, corticosteroids, and anti-interleukin-1 therapy. This study aimed to share our experiences of PFMS so as to shed light on this rare and elusive condition.

Methods: This cross-sectional analysis included 17 patients diagnosed with PFMS at our pediatric rheumatology clinic between January 2018 and September 2023.

Results: In our clinic, 17 (1%) of 1663 familial Mediterranean fever patients presented with PFMS, and it was the initial manifestation in 10 patients (58.8%) in the cohort. Eight of the 17 patients had an M694V homozygous mutation in the MEFV gene. A magnetic resonance imaging showed myositis and fasciitis in just 1 patient, and myositis alone was evident in 5 others. Symptoms improved in 2 patients with nonsteroidal anti-inflammatory drugs, whereas prednisolone improved symptoms in 12 patients and anakinra was required in 3 patients. Patients who received anakinra had another severe attack and required long-term anakinra or canakinumab.

Conclusions: Syndrome for PFMS is difficult to recognize as it can sometimes be the first manifestation of familial Mediterranean fever. The syndrome is not accompanied by fever in some patients, even though the word febrile is part of its name. Most patients respond dramatically to nonsteroidal anti-inflammatory drugs or corticosteroids. In some patients with PFMS, long-term anakinra or canakinumab treatment may be more useful in preventing severe attacks of PFMS than short-term (5 to 7 days) anakinra treatment.