Biallelic pathogenic variants in the MBD4 gene have recently been associated with an autosomal recessive cancer predisposition syndrome deemed “ MBD4 -associated neoplasia syndrome (MANS)”. Early reports of individuals with MANS highlight the propensity to develop young onset colorectal polyposis and hyper-mutated acute myeloid leukemia (AML). In the following case series, we present four patients with MANS from three families...