GCH1 and microcephaly: The features that were more common in the PEDIATAX cohort than in the literature cohort included athetosis, hypotonia, spasticity, and ophthalmological findings with ANO3; developmental delay and epilepsy with FXN; ataxia and spasticity with GCH1; ataxia with MTM1; muscle weakness with RARS2; microcephaly and tremor with SLC2A1; multiorgan involvement, intellectual disability, and seizures with SLC17A5; ataxia and multiorgan involvement with SPAST; and intellectual disability, ophthalmological findings, and hearing loss with TWNK.