PMS2 - Mutations

Mutations

PMS2 is a gene that encodes for DNA repair proteins involved in mismatch repair. The PMS2 gene is located on chromosome 7p22 and it consists of 15 exons. Exon 11 of the PMS2 gene has a coding repeat of eight adenosines.

Heterozygous germline mutations in DNA mismatch repair genes like PMS2 lead to autosomal dominant Lynch syndrome. Only 2% of families that have Lynch syndrome have mutations in the PMS2 gene. The age of patients when they first presented with PMS2-associated Lynch syndrome varies greatly, with a reported range of 23 to 77 years.

In rare cases, a homozygous defect may cause this syndrome. In such cases a child inherits the gene mutation from both parents and the condition is called Turcot syndrome or Constitutional MMR Deficiency (CMMR-D). Up until 2011, 36 patients with brain tumors due to biallelic PMS2 germline mutations have been reported. Inheritance of Turcot syndrome can be dominant or recessive. Recessive inheritance of Turcot syndrome is caused by compound heterozygous mutations in PMS2. 31 out of 57 families reported with CMMR-D have germline PMS2 mutations. 19 out of 60 PMS2 homozygous or compound heterozygous mutation carriers had gastrointestinal cancer or adenomas as the first manifestation of CMMR-D. Presence of pseudogenes can cause confusion when identifying mutations in PMS2, leading to false positive conclusions of the presence of mutated PMS2.

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