OBJECTIVETo characterize the clinical features of Chinese HNPCC families and to screen the mutations of a poly-(A)8 tract in M3 cholinergic receptor gene in these families.

METHODSThe clinical features of 15 Chinese HNPCC families were characterized. Genomic DNAs from 15 probands were prepared. PCR and direct DNA sequencing analysis were employed to examine the mutations of a poly-(A)8 tract in exon 8 of M3 cholinergic receptor gene.

RESULTSTotal 55 cancer patients were found in 15 families including 41 cases of colorectal carcinoma with an average of 2.73 colorectal carcinomas developed per family. Thirty out of forty-one (73%) patients were diagnosed before age of 50 years. Proximal colon was involved in 51% of patients, while anus and rectum were 40 %. Synchronous and metachronous multiple colorectal cancers developed in 5 patients (12%). Two thirds of families belonged to Lynch II syndrome, and total 18 extracolonic malignancies in 14 patients were identified. Gastric carcinoma was the most common extracolonic types. In 15 HNPCC probands, no mutation was detected in the poly-(A)8 tract of exon 8 of M3 cholinergic receptor gene.

CONCLUSIONM3 cholinergic receptor gene might have little relation with HNPCC in Chinese population. The criteria for Chinese HNPCC are useful and practical in clinical application.