Genetics, clinical manifestations and management of FAP and HNPCC.

Colorectal cancer occurs in the familial cancer syndromes in about 2 to 4 percent. The major genetic syndromes are Familial adenomatous polyposis (FAP) and Hereditary nonpolyposis colorectal cancer (HNPCC). FAP is caused by germline mutation of APC gene, and HNPCC is caused by germline mutation in one of five MMR genes. The identification of patients with inherited disease is very important in the management of colorectal cancer. But, it is impractical to test every patient with the disease for these mutations. The clinical and genetical screening programme should be advised for family members at risk and colectomy in affected individuals in purpose to reduce the frequency of colorectal cancer.