BDP1 and spinocerebellar ataxia type 17: Variants in BRF1, a subunit of TFIIIB, result in cerebellofaciodental syndrome, which is characterized by intellectual disability, speech impairment, craniofacial abnormalities, dental anomalies, short stature and cerebellar hypoplasia.28  De novo repeat expansions in TBP, another TFIIIB subunit, cause spinocerebellar ataxia type 17.29 Additionally, variants in BDP1, the third subunit of TFIIIB, have been associated with hereditary hearing loss.30