Abstract 35: Novel genetic and clinical determinants of Constitutional Mismatch Repair Deficiency syndrome: Report from the CMMRD consortium

Purpose: Constitutional mismatch repair deficiency (CMMRD) is a devastating cancer predisposition syndrome affecting children born with two mutated alleles in one of four mismatch repair genes. Data regarding clinical manifestations, molecular screening tools and management are limited. Patients and methods: We established an international CMMRD consortium and collected comprehensive clinical and genetic data. Molecular diagnosis of tumor and germline biospecimens were performed. A surveillance protocol was developed and implemented. Results: Overall, 27/30 (90%) of children with CMMR-D developed 48 different tumors. While childhood CMMR-D related tumors were observed in all families, Lynch related tumors in adults were observed in only 2/17 families (p