Homozygous variants in this gene were previously linked to progressive cerebellar atrophy and polyneuropathy [6] and recently, to both severe ataxia with oculomotor apraxia 4 (AOA4, MIM 616267) or microcephaly with seizures and developmental delay (MCSZ, MIM 613402) [7]. The gene discussed is PNKP; the disease is Global developmental delay.