library_construction_protocol: Genomic DNA from a total of 20 samples from patients with a germline KMT2B or KMT2D variant was extracted from peripheral blood using Gentra Puregene Blood Kit (Qiagen) or other standard methods and quantified by Qubit™ dsDNA BR Assay Kit (Invitrogen, ThermoFisher). All DNA Samples were sequenced on an Illumina HiSeq 4000 analyser (Illumina, San Diego, CA) using TruSeq® Methyl Capture EPIC kit. Bisulfite conversion, library preparation, target enrichment and sequencing were performed at the Cambridge University Department of Medical Genetics Stratified Medicine Core Laboratory (SMCL).