Low serum level of high‐sensitivity C‐reactive protein in a Japanese patient with maturity‐onset diabetes of the young type 3 (MODY3)

High‐sensitivity C‐reactive protein (hs‐CRP) levels in European populations are lower in patients with maturity‐onset diabetes of the young type 3 (MODY3) than in those with type 2 diabetes. hs‐CRP levels have been suggested to be useful for discriminating MODY3 from type 2 diabetes. As hs‐CRP levels are influenced by various factors including race and body mass index, it is worthwhile to examine whether hs‐CRP can serve as a biomarker for MODY3 in Japanese. Here we describe the case of a Japanese MODY3 patient with a nonsense mutation in the HNF1A gene. Two measurements showed consistently lower hs‐CRP levels (<0.05 and 0.09 mg/L) than in Japanese patients with type 1 and type 2 diabetes. Hepatic expression of Crp messenger ribonucleic acid was significantly decreased in Hnf1a knockout mice. The hs‐CRP level might be a useful biomarker for MODY3 in both Japanese and European populations.