Although current literature on the risk of CRC development in carriers of pathogenic BLM alleles is contradictory [14–16], we recently found by targeted re-sequencing of a validation cohort that monoallelic pathogenic BLM variants were enriched in these cases.[17] ATM is involved in double-strand break repair and mutations in its encoding gene are associated with ataxia telangiectasia, another autosomal recessive disorder. Here, BLM is linked to ataxia telangiectasia.