RARS2 and pontocerebellar hypoplasia: We agree with efforts to associate types of PCH by genetic aetiology, as in ‘TSEN mutation spectrum disorders’ (to include PCH Types 2, 4 and 5),74 or to classify PCH Type 6 as a RARS2-associated phenotype with early onset mitochondrial encephalopathy.70 As such, we propose the introduction of a dyadic naming strategy (e.g. RARS2-associated PHSD) to replace the naming conventions that rely on numerical designations (e.g. PCH 1, PCH 2).