CONSTITUTIONAL MISMATCH REPAIR DEFICIENCY (CMMRD), ALSO KNOWN AS AUTOSOMAL RECESSIVE CHILDHOOD CANCER PREDISPOSITION SYNDROME
It has become appreciated that biallelic mutations in MLH1, MSH2, MSH6, and most commonly, PMS2 can be responsible for an autosomal recessive condition characterized by mainly childhood and adolescent malignancies, particularly hematological (lymphomas and leukemias) and brain Tumours, including medulloblastomas, glioblastomas, and oligodendrogliomata, other cancers (GI or uterine cancer), and dermatological features of NF (café-au- lait patches) (De Vos et al. 2004; Menko et al. 2004; reviewed in Wimmer and Etzler 2008). This has in the past been described as a variant of Turcot syndrome (De Rosa et al. 2000; Bougeard et al. 2003), and it is interesting to speculate what proportion of Turcot syndrome is attributable to mutations in APC and the MMR genes, particularly as both autosomal dominant and recessive forms of Turcot syndrome have been described.