Lichen Sclerosus in a Patient With a History of Hereditary Nonpolyposis Colorectal Cancer

Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer, is an autosomal dominant genetic syndrome caused by germline mutations in 1 or more of the mismatch repair genes, including MLH1, MSH2, MSH6 or PMS2 or all these (Table). The DNA mismatch repair plays an essential role in the maintenance of genome stability as a postreplicative system that repairs normal or damaged single-base mismatches, as well as insertions and deletions in the DNA. A heterozygous germline genetic mutation at 1 of these sites leads to microsatellite instability (MSI), a phenomenon of genetic hypermutability that predisposes one to develop errors in the DNA replication process. Regular dermatologic follow-up is recommended as these patients may develop a number of cutaneous malignancies, establishing patients with Lynch syndrome with an additional diagnosis of Muir-Torre syndrome (MTS). A phenotypic variant of Lynch syndrome, MTS is diagnosed when a patient has 1 of any number of typical hereditary nonpolyposis colorectal cancer tumors including colon, endometrial, urologic, small bowel, ovarian, hepatobiliary and brain, in addition to a sebaceous gland tumor (adenoma, epithelioma or carcinoma). Sebaceous adenomas are the most frequent skin lesions found in patients with MTS, and they present as yellow papules or nodules most commonly localized on the face.