The Five Genes Behind Lynch Syndrome
[ MLH1 · MSH2 · MSH6 · PMS2 · EPCAM ]Lynch syndrome is the most common hereditary colorectal cancer syndrome — and one of the most underdiagnosed. Published prevalence studies estimate roughly 1 in 279 people carry a Lynch-associated variant, yet the vast majority don’t know it. It is caused by inherited mutations in DNA mismatch repair (MMR) genes — the cellular proofreaders that fix copying errors every time a cell divides.
The Most Common Culprit
Together with MSH2, accounts for the majority of Lynch syndrome cases. MLH1 carriers tend toward earlier-onset colorectal cancer.
High Penetrance
Comparable lifetime risk to MLH1, with elevated rates of endometrial, ovarian, and urinary tract cancers alongside colorectal.
Later Onset, Endometrial Focus
Often presents later in life, with endometrial cancer frequently the first sign — one reason Lynch is under-recognized in women.
Lower But Real Penetrance
Historically underestimated; carrier risks are more modest but still far above population baseline, especially for colorectal and endometrial cancer.
The Indirect Disruptor
Deletions in EPCAM silence the neighboring MSH2 gene — a reminder that Lynch genetics isn’t limited to the four MMR genes themselves.
Silent Until It Isn’t
MMR-deficient tumors develop quickly once started, which is exactly why surveillance intervals are tight: 1–2 years, not 10.
The Numbers: Risk With And Without Lynch
[ Published Figures ]| Cancer Type | General Population Risk | Lynch Syndrome Lifetime Risk |
|---|---|---|
| Colorectal | ~4% | Up to 80% (varies by gene; MLH1/MSH2 highest) |
| Endometrial | ~3% | Up to ~60% — often the first cancer diagnosed in women with Lynch |
| Ovarian | ~1.3% | Elevated — up to ~10–12% in some series |
| Stomach / small bowel / urothelial | Low single digits | Elevated several-fold; screening individualized by NCCN guidance |
A 50% inheritance pattern applies to every child of a carrier. One positive result can redirect screening for an entire family — see our guide to what happens after a positive result.
Surveillance: Why Known Lynch Is Manageable Lynch
[ NCCN-Aligned Schedule ]Here is the part most people miss: Lynch syndrome is dangerous when unknown and highly manageable when known. With NCCN-aligned surveillance, most Lynch-related cancers are caught early and treated successfully.
Colonoscopy Every 1–2 Years
Not every 10 years — every 1–2, beginning at 20–25 (or 2–5 years before the earliest family diagnosis). This single change transforms outcomes: polyps are removed before MMR-deficient cells can accelerate.
Endometrial Surveillance
Annual endometrial biopsy or ultrasound discussion from 30–35, plus awareness education. Risk-reducing hysterectomy is discussed after childbearing.
Aspirin & Lifestyle
Published trials support daily aspirin reducing colorectal cancer incidence in Lynch carriers — a decision to make with your doctor, alongside weight, exercise, and smoking cessation.
1 In 279 People Carry It. Know Which One You Are.
[ GeneCancer · 108 Genes ]
The GeneCancer panel covers all five Lynch syndrome genes plus BRCA1/2 and 100+ more — from an at-home cheek swab at up to 99.9% analytical accuracy. Results in 5–7 days (48-hour priority available), counselor included with positive results. $499 one-time, or $89/mo with all 11 tests ($59/mo billed annually, $712/yr). 30-day money-back guarantee.
Lynch Syndrome — FAQs
Lynch syndrome is caused by inherited pathogenic variants in the DNA mismatch repair genes MLH1, MSH2, MSH6, and PMS2, or by deletions in EPCAM that silence MSH2. These genes normally fix DNA copying errors; when one copy is broken from birth, errors accumulate faster and cancer risk rises sharply.
Published prevalence studies estimate roughly 1 in 279 people carries a Lynch-associated variant — making it one of the most common hereditary cancer syndromes. Most carriers are unaware, because families often attribute repeated cancers to bad luck rather than genetics.
Up to 80% lifetime, depending on the gene involved (MLH1 and MSH2 carry the highest risk), versus roughly 4% in the general population. That number sounds frightening, but it assumes no surveillance — with colonoscopy every 1–2 years starting at 20–25, most Lynch-related cancers are prevented or caught early.
No. Endometrial cancer risk in women rises to up to ~60%, and ovarian, stomach, small bowel, urinary tract, and certain other cancers are also elevated. Women with Lynch are often diagnosed first through endometrial cancer, not colorectal.
By germline genetic testing of the MMR genes and EPCAM — included in the GeneCancer 108-gene panel from an at-home cheek swab, with results in 5–7 days (48-hour priority available) and a genetic counselor session with every positive result. $499 one-time or included with the $89/month membership.
Yes. Each first-degree relative has a 50% chance of carrying the same variant. Cascade testing for a known family variant is faster and less expensive, and it directly determines who needs intensive colonoscopy surveillance and who can follow standard screening.