POLR3A and Hypomyelinating leukodystrophy with or without oligondontia and/or hypogonadism: Hypomyelinating leukodystrophy 7 (HLD7) is an autosomal recessive oligodendroglial cell-related myelin disease, which is associated with some nucleotide mutations of the RNA polymerase 3 subunit a (polr3a) gene.