Abstract
BackgroundWe showed previously that Japanese individuals with familial Mediterranean fever (FMF) have a more atypical phenotype compared to endemic areas. The clinical differences between young-onset FMF (YOFMF), adult-onset FMF (AOFMF), and late-onset FMF (LOFMF) in Japan are unclear.MethodsWe enrolled 395 consecutive patients. We defined YOFMF, AOFMF, and LOFMF as the onset of FMF at < 20, 20–39, and ≥ 40 years of age, respectively. We compared clinical manifestations and MEFV mutations patterns among these groups.ResultsMedian ages at onset were YOFMF 12.5 years (n = 182), AOFMF 28 years (n = 115), and LOFMF 51 years (n = 90). A family history, MEFV mutations in exon 10, and more than two MEFV mutations were significantly more frequent in the earlier-onset groups (p < 0.01, p < 0.0001, and p < 0.001, respectively). In the accompanying manifestations, thoracic and abdominal pain were significantly more frequent in the earlier-onset groups (p < 0.01 and p < 0.0001, respectively), whereas arthritis and myalgia were significantly more frequent in the later-onset groups (p < 0.0001 and p < 0.01, respectively). The multiple logistic regression analysis revealed that the presence of MEFV exon 10 mutations and earlier onset were significantly associated with serositis, whereas the absence of MEFV exon 10 mutations, later onset, and the presence of erysipelas-like erythema were significantly associated with musculoskeletal manifestations. There was no significant between-group difference in the responsiveness to colchicine.ConclusionsOur results indicate that the later-onset FMF patients had a lower percentage of MEFV mutations in exon 10 and predominantly presented arthritis and myalgia. It is important to distinguish their FMF from other inflammatory diseases.
Highlights
We showed previously that Japanese individuals with familial Mediterranean fever (FMF) have a more atypical phenotype compared to endemic areas
FMF is characterized by recurrent and self-limiting fever attacks in a short period accompanied by serositis manifestations including peritonitis and pleuritis, musculoskeletal manifestations including synovitis and myalgia, and skin manifestations including erysipelas-like skin lesions [3,4,5,6]
According to the Tel Hashomer criteria, a typical case is characterized by fever attacks of ≥ 38.0 °C and lasting 12–72 h accompanied by pleuritis, nonlocalized peritonitis, and monoarthritis of the hip, knee, or ankle [7], whereas an atypical case is characterized by fever attacks of < 38.0 °C, lasting only a short period (i.e., 6–12 h) or lasting a long period (72 h–7 days), abdominal pain without definitive peritonitis, localized peritonitis, or arthritis outside the typical sites [7]
Summary
We showed previously that Japanese individuals with familial Mediterranean fever (FMF) have a more atypical phenotype compared to endemic areas. Japanese FMF cases with MEFV mutations were described for the first time in 2002 [13], and there is accumulating evidence showing the characteristics of FMF in Japan [9, 14,15,16,17,18,19]. The frequency of FMF cases with high-penetrance MEFV mutations such as exon 10 is lower in Japan than in Western countries, and FMF cases in Japan have been reported to more often be adult onset and to more often show atypical clinical symptoms [9]. Because of the misunderstanding that FMF is rare in Japan, or that there is a higher percentage of earlier onset in Japan, it is possible that the condition’s diagnosis has been delayed [16]
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