Corticosteroid-resistant anakinra-responsive protracted febrile myalgia syndrome as the first manifestation of familial Mediterranean fever

Abstract

Familial Mediterranean fever (FMF) is the most common type of monogenic periodic fever syndromes and characterized by recurrent self-limited attacks of fever and polyserositis. Musculoskeletal signs and symptoms are not uncommon and manifested as arthritis and myalgia. Myalgia may be spontaneous or exercise-induced that mostly affects lower limbs and spontaneously resolves in 2-3 days. Protracted febrile myalgia syndrome (PFMS) is another form of rare and severe muscle involvement in FMF. PFMS affects all muscle groups and lasts for several weeks. Herein we present a pediatric case of PFMS that presented as the first manifestation of FMF, not responded to prednisolone at all but showed dramatic improvement with anakinra. Our case has a few distinctive points. She did not have a diagnosis of FMF and also she did not have any previous complaints compatible with FMF. Thus, PFMS was the first sign of FMF in this patient. Most of the cases of PFMS show dramatic response to corticosteroids, but our case did not respond at all to high-dose corticosteroids and anakinra resulted in rapid resolution of the symptoms. Protracted febrile myalgia syndrome may be the first manifestation of FMF. It should be suspected in cases with prolonged and unexplained fever, severe myalgia, and high acute phase reactants.