Variables for differential diagnosis of familial Mediterranean fever: multiple correspondence analysis of a large Japanese cohort.

OBJECTIVES: We investigated differential diagnoses that should be noted with familial Mediterranean fever (FMF) and useful variables for differentiation in a large Japanese cohort. METHODS: Patients aged ≥13 years who were clinically suspected of having FMF by Livneh criteria were studied 1 year after MEFV genetic testing. Patients ultimately diagnosed with other diseases were studied, and the association among each disease, patient characteristics, and clinical variables were analyzed using multiple correspondence analysis. RESULTS: In total, 504 patients were included in this study; 34 (6.7%) were diagnosed with a disease other than FMF. The most common diagnosis was Behçet's disease, followed by periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome, inflammatory bowel disease, myelodysplastic syndromes (MDS), and infectious diseases. Although none of the non-FMF patients had exon 10 variants, some responded to colchicine treatment. Multiple correspondence analysis suggested that atypical symptoms such as stomatitis were associated with Behçet's disease and PFAPA syndrome, whereas characteristic situations such as disease onset ≥40 years were associated with MDS and infectious diseases. CONCLUSION: Careful follow-ups and reanalysis of the diagnosis should be performed for patients with atypical findings and no exon 10 variants, even if their symptoms meet the clinical criteria for FMF.