Lynch syndrome 2 (Monarch Disease Ontology id MONDO_0012249) is an autosomal dominant hereditary neoplastic syndrome caused by pathogenic variants in the MLH1 mismatch repair gene. It is characterized by an increased risk of colorectal cancer in the absence of extensive polyposis, endometrial, ovarian, gastric, small intestinal, and urinary tract cancers, often occurring at younger ages. Also known as: Hereditary non-polyposis colon cancer type 2, Hereditary nonpolyposis colorectal cancer type 2, Lynch 2 syndrome, MLH1-related Lynch syndrome, colorectal cancer, hereditary nonpolyposis, type 2, familial non-polyposis colon cancer type 2.