Constitutional mismatch repair deficiency in childhood colorectal cancer harboring a de novo variant in the MSH6 gene: a case report.

We present the first report of a CMMRD patient with a de novo variant in MSH6, who developed colorectal cancer in childhood. CMMRD symptoms often resemble NF1, as observed here. Physicians should become familiar with CMMRD clinical phenotypes for the screening and early detection of cancer.