Constitutional mismatch repair deficiency in a healthy child: on the spot diagnosis?

We report of a case of a healthy six-year-old girl who fulfilled the diagnostic criteria of NF1 with >6 CALM and freckling. Since molecular genetic testing was unable to confirm the diagnosis of NF1 or Legius syndrome and the patient was a child of consanguineous parents, we suspected CMMRD and found a homozygous PMS2 mutation that impairs MMR function. Current guidelines advise testing for CMMRD only in cancer patients. However, this case illustrates that including CMMRD in the differential diagnosis in suspected sporadic NF1 without causative NF1 or SPRED1 mutations may facilitate identification of CMMRD prior to cancer development. We discuss the advantages and potential risks of this CMMRD testing scenario. PMID: 28503822 [PubMed - as supplied by publisher]
Source: Clinical Genetics - Category: Genetics & Stem Cells Authors: Tags: Clin Genet Source Type: research