Hypomyelinating leukodystrophy disorder in which is caused of the disease is a variation in any of the genes encoding POLR3 (RNA polymerase III) subunits, including POLR3A, POLR3B and POLR1C. This disorder is characterized by the association of dental abnormalities (delayed dentition, abnormal order of dentition, hypodontia), hypogonadotropic hypogonadism, and hypomyelinating leukodystrophy manifesting with neurodevelopmental delay or regression and/or progressive cerebellar symptoms.