Concomitant IDH-wildtype glioblastoma and IDH1-mutant anaplastic astrocytoma in a patient with constitutional mismatch repair deficiency syndrome.

Constitutional mismatch repair deficiency (CMMRD) is a rare and often under-recognized tumour predisposition syndrome, presenting with both extracranial and malignant brain tumours that occur in children and/or young adults [1]. The genetic defects underlying this disease are biallelic germline mutations in one of the DNA mismatch repair (MMR) genes leading to a constitutional DNA repair defect that causes a cancer predisposition syndrome with early onset [2]. This mechanism is different from Lynch syndrome (LS) where a heterozygous germline loss-of-function mutation is observed and the patients are more prone to develop colon and genitourinary cancers as adults [1]. This article is protected by copyright. All rights reserved.