Effectiveness of Colchicine or Canakinumab in Japanese Patients with Familial Mediterranean Fever: A Single-Center...

Background: To investigate the clinical features of Japanese patients with Familial Mediterranean Fever (FMF), we evaluated the frequency of attacks, treatment responses, and adverse effects in 27 patients with FMF treated with colchicine or canakinumab in a real-world clinical setting. Methods: We retrospectively reviewed 27 Japanese patients with FMF treated at our institute between April 2012 and June 2023. All patients were diagnosed with FMF according to the Tel-Hashomer criteria. We performed genetic analyses of the MEFV gene using targeted next-generation sequencing. The clinical response was monitored through the number of attacks, and inflammatory markers were monitored through the C-reactive protein (CRP), and serum amyloid A (SAA) concentrations. Colchicine resistance was defined as the presence of at least one attack/month despite administration of the maximum tolerated dose of colchicine for at least 6 months, and C-reactive protein and serum amyloid A levels above the normal range between attacks. Results: A total of 27 patients diagnosed with FMF were enrolled in this study and the median follow-up period was 36.4 months. The median attack frequency was 1.0 (interquartile range: 0.33-1.0) every 3 months before treatment initiation. All the patients (n = 27) were treated with colchicine. Among the 27 patients, 20 (71.8%) showed a clinical response and 7 (25.9%) showed an incomplete response with sufficient doses of colchicine (n = 5) and non-sufficient doses (n = 2). Two patients on non-sufficient doses were unable to increase colchicine to the maximum dose due to diarrhea and liver dysfunction. All seven patients achieved a reduction in attack frequency after the initiation of canakinumab. No serious adverse events associated with canakinumab treatment were observed. In these seven patients with colchicine-resistant FMF (crFMF), the MEFV exon 10 variant was not detected, and the absence ratio of the MEFV variant was significantly higher compared to those without crFMF. Conclusions: Colchicine was effective in 71.8% (20/27) of Japanese patients with FMF; however, the remaining patients (7/27) had crFMF. Canakinumab effectively controlled febrile attacks in crFMF, even in the absence of pathogenic MEFV exon 10 variants.