Lynch syndrome

Lynch syndrome is an inherited condition in which the cell's spell-checker for DNA is weakened, so typos in the genetic text go uncorrected. Imagine a proofreader who keeps missing the same kinds of small errors; over years these slip-ups build up in the lining of the bowel and elsewhere, raising the risk that a cell turns cancerous.

The weakened spell-checker is the DNA mismatch repair system, which normally fixes the small insertion and deletion errors made while copying DNA. Lynch syndrome is caused by inheriting a faulty copy of a mismatch-repair gene, such as MLH1, MSH2, MSH6, or PMS2. When the second copy is lost in a cell, repair fails and mutations accumulate quickly, a state visible as microsatellite instability.

Lynch syndrome chiefly raises lifetime risk of colorectal cancer, along with endometrial and several other cancers, often at younger ages than usual. It is typically inherited in an autosomal dominant pattern. Recognizing it allows for tailored, earlier screening through genetic counseling; it is a strong predisposition managed medically, not a guaranteed outcome.