Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PVS1PM2PP5
The ENST00000231790.8(MLH1):c.551C>A(p.Ser184Ter) variant causes a stop gained change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in Lovd as Pathogenic (no stars). Synonymous variant affecting the same amino acid position (i.e. S184S) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.
MLH1 (HGNC:7127): (mutL homolog 1) The protein encoded by this gene can heterodimerize with mismatch repair endonuclease PMS2 to form MutL alpha, part of the DNA mismatch repair system. When MutL alpha is bound by MutS beta and some accessory proteins, the PMS2 subunit of MutL alpha introduces a single-strand break near DNA mismatches, providing an entry point for exonuclease degradation. The encoded protein is also involved in DNA damage signaling and can heterodimerize with DNA mismatch repair protein MLH3 to form MutL gamma, which is involved in meiosis. This gene was identified as a locus frequently mutated in hereditary nonpolyposis colon cancer (HNPCC). [provided by RefSeq, Aug 2017]