Late-onset familial Mediterranean fever: A case series of missed diagnoses in pleural effusions.

Familial Mediterranean fever (FMF) is an autoinflammatory disorder with typical early onset and recurrent episodes of fever and serositis. Late-onset FMF, especially presenting as isolated pleural effusion, is rare and often misdiagnosed. We present a case series of six patients over the age of 50 who were diagnosed with FMF after presenting with unexplained pleural effusions. Conventional evaluations failed to identify alternative etiologies, and empirical therapies showed limited success. In all cases, MEFV (Mediterranean fever) gene analysis revealed R202Q mutations, which guided the initiation of colchicine therapy with favorable outcomes. This study highlights the diagnostic challenges posed by atypical FMF presentations and underscores the importance of considering FMF in recurrent serositis, even without systemic inflammation. Early genetic testing and appropriate treatment may reduce unnecessary interventions and improve patient outcomes.