label: Lynch 1 Syndrome
label_lc: lynch 1 syndrome
description: A rare genetic neoplastic syndrome with an autosomal dominant pattern of inheritance but incomplete penetrance. It is associated with a greater than 70 % risk of developing colorectal carcinoma. It is caused by a mutation in one of the mismatch repair genes: MSH2, MLH1, MSH6 or PMS2. It usually manifests at age 50 or younger with multiple synchronous or metachronous colorectal carcinomas. Clinical course is rapidly progressive. Prognosis is variable with a high risk for the development of additional colorectal carcinomas. However, survival is significantly better than non-HNPCC carcinomas of equivalent stage.