Modifier genes and Lynch syndrome: some considerations.

Lynch Syndrome (LS) is a highly variable entity with some patients presenting at very young ages with malignancy whereas others may never develop a malignancy yet carry an unequivocal genetic predisposition to disease. The most frequent LS malignancy remains colorectal cancer, a disease that is thought to involve genetic as well as environmental factors in its aetiology. Environmental insults are undeniably associated with cancer risk, especially those imparted by such activities as smoking and excessive alcohol consumption. Notwithstanding, in an inherited predisposition the expected exposures to an environmental insult are considered to be complex and require knowledge about the respective exposure and how it might interact with a genetic predisposition. Typically, smoking is one of the major confounders when considering environmental factors that can influence disease expression on a background of significant genetic risk. In addition to environmental triggers, the risk of developing a malignancy for people carrying an inherited predisposition to disease can be influenced by additional genetic factors that do not necessarily segregate with a disease predisposition allele. The purpose of this review is to examine the current state of modifier gene detection in people with a genetic predisposition to develop LS and present some data that supports the notion that modifier genes are gene specific thus explaining why some modifier gene studies have failed to identify associations when this is not taken into account.