Unprecedented Coexistence of Autoinflammatory Myositis and Chronic Thrombosis with heterozygotic M694V mutation: An atypical presentation of Familial Mediterranean Fever.

Abstract

Familial Mediterranean Fever (FMF) is a hereditary autoinflammatory disorder predominantly characterized by periodic fever, abdominal pain, and joint manifestations. It can exhibit various atypical presentations and affects individuals globally. However, cases of FMF concurrently presenting with chronic thrombosis and myositis have not been previously reported. A 41-year-old male presented with alternating severe bilateral leg pain, stiffness, and localized swellings without fever or abdominal symptoms. His history included recurrent inflammatory joint pain treated with prednisolone. Physical examination revealed leg pain, limited ankle joint movement, and tender swellings in thighs, forearms, and feet. Collateral abdominal veins were also observed. Unresponsive to prednisolone and colchicine, the patient underwent MRI, revealing muscle inflammation in both legs and thighs and chronic thrombosis in the infrarenal inferior vena cava. Genetic testing confirmed the heterozygotic M694V mutation, diagnosing an atypical FMF. Anakinra treatment led to substantial clinical and laboratory improvement. Although FMF diagnosis typically relies on characteristic clinical features and genetic analysis, atypical presentations challenge established criteria. This case uniquely showcases coexisting myositis and chronic thrombosis in FMF. Myalgia is common in FMF, with M694V mutation associated with severe muscular symptoms. The lack of fever and myositis findings differentiate our case from protracted febrile myalgia syndrome. FMF's chronic inflammatory state is known to influence thrombosis risk, and our findings align with this association. Chronic thromboembolism and myositis together signify an unusual clinical presentation of FMF. This case highlights the potential for FMF to present with complex manifestations beyond the conventional symptoms. Myositis and vascular involvement should prompt consideration of FMF diagnosis when combined with patient history, clinical features, and laboratory results. These rare associations underscore the need for further research to enhance understanding of FMF's diverse clinical spectrum.