Germline mutations of the MYH gene in Japanese patients with multiple colorectal adenomas

Germline mutations of the MYH gene have been revealed to associate with the recessive inheritance of multiple colorectal adenomas in Caucasian population. However, MYH mutations in Japanese patients have not yet been clarified. In an assessment of MYH mutations, we examined 35 Japanese patients with multiple colorectal adenomas who had neither dominant inheritance of colorectal tumors, nor germline APC mutations. One patient had a homozygous biallelic MYH mutation, R231C and three independent patients had monoallelic MYH mutations at a splice-site on exon 11 (IVS10-2 A to G). These four patients had 21 to around 100 colorectal adenomas and 1-3 synchronous colorectal carcinomas. The most common mutations in Caucasian patients, Y165C and G382D, were not detected in our Japanese cases. The MYH mutations detected in Japanese patients were novel and different from those detected among Caucasian, Indian and Pakistani patients, which suggests the existence of ethnic differentiation in MYH mutations.