Among the 26 types of established HLD recorded in the Online Mendelian Inheritance in Man (OMIM) database, HLD-23 is caused by mutations of the gene RNF220 (RING finger protein 220) (15), which encodes a RING-type E3 ubiquitin ligase. This evidence concerns the gene RNF220 and leukodystrophy, hypomyelinating, 23, with ataxia, deafness, liver dysfunction, and dilated cardiomyopathy.