In addition to a mutation in exon 15 of the POLR3B gene, which is relatively common amongst patients with 4H leukodystrophy caused by POLR3B mutations, our patient also has a unique intronic mutation at intron 24 [5], which has not been described in others with 4H leukodystrophy. This evidence concerns the gene POLR3B and leukodystrophy.