Of the Pol III subunits implicated in POLR3-HLD disease, pathogenic variants in POLR3K are rare, with only two patients previously described in the literature, both males from two unrelated consanguineous families who both harboured the same homozygous variant (c.121C>T; p.R41W) [6]. The gene discussed is POLR3K; the disease is leukodystrophy.