Autosomal recessive
Caused by changes in both copies of POLR3A, which encodes the largest subunit of RNA polymerase III, an enzyme that makes transfer RNAs and other small RNAs. Each parent usually carries one changed copy.
Signs and symptoms
One recognised form is 4H leukodystrophy, with hypomyelination of the brain causing unsteadiness and tremor from childhood, together with missing or late teeth and delayed puberty from hypogonadism. Some people instead develop spastic ataxia in adolescence or adulthood. It has also been reported in one infant with Wiedemann-Rautenstrauch syndrome, a severe neonatal progeroid condition, which needs confirmation.
What a diagnosis changes
Neurological, physiotherapy, dental and endocrine care, including hormone treatment to induce puberty when needed, and eye review for myopia. Genetic counselling and carrier testing of relatives clarify recurrence risk.
Genes analysed
Includes 6 related subtypes ↓Hide subtypes ↑
- hypomyelinating leukodystrophy-ataxia-hypodontia-hypomyelination syndrome
- hypomyelination-cerebellar atrophy-hypoplasia of the corpus callosum syndrome
- leukodystrophy, hypomyelinating, 7, with or without oligodontia and/or hypogonadotropic hypogonadism
- odontoleukodystrophy
- tremor-ataxia-central hypomyelination syndrome
- Wiedemann-Rautenstrauch syndrome
