Recessive mutations in POLR3B, encoding the second largest subunit of Pol III, cause a rare hypomyelinating leukodystrophy

Mutations in POLR3A encoding the largest subunit of RNA polymerase Ill (Pol III) were found to be responsible for the majority of cases presenting with three clinically overlapping hypomyelinating leukodystrophy phenotypes. We uncovered in three cases without POLR3A mutation recessive mutations in POLR3B, which codes for the second largest subunit of Pol III. Mutations in genes coding for Pol III subunits are a major cause of childhood-onset hypomyelinating leukodystrophies with prominent cerebellar dysfunction, oligodontia, and hypogonadotropic hypogonadism.