Coexistence of Mixed Connective Tissue Disease and Familial Mediterranean Fever in a Japanese Patient.

We herein report a Japanese patient with familial Mediterranean fever (FMF) who developed the clinical manifestations of mixed connective tissue disease (MCTD) and Sjögren's syndrome. The patient was a 36-year-old woman presenting with a periodic short-duration (2-3 days) fever and pleural pain. An Mediterranean fever (MEFV) gene analysis detected a complex allele mutation (P369S/R408Q) in exon 3 of the MEFV gene. Serological and clinical data showed the coexistence of MCTD and Sjögren's syndrome. Treatment with colchicine (1.0 mg/day) successfully eliminated febrile attack and pleuritis, leading to the diagnosis of FMF. Four months after the initiation of colchicine treatment, she presented with MCTD-related pulmonary artery hypertension. This is the first report of FMF coexisting with MCTD.