Mutations in RNA polymerase III subunit A and B (POLR3A/B) result in the 4H syndrome (Hypomyelination, Hypodontia and Hypogonadotropic Hypogonadism) (Wolf et al., 2014) whilst those in Ring finger protein 216 (RNF216), OTU deubiquitinase 4 (OTUD4) and Patatin like phospholipase domain containing 6 (PNPLA6) produce the phenotypic combination of HH and ataxia (also known as Gordon-Holmes syndrome) (Margolin et al., 2013; Topaloglu et al., 2014). The gene discussed is OTUD4; the disease is tooth agenesis.