PNKP and Global developmental delay: Mutations in PNKP have been found to be responsible for three different relatively rare neurological diseases: an autosomal recessive neurodegenerative disease Ataxia-ocular motor apraxia 4 (AOA4)1–6, a variant of the hereditary peripheral neuropathy Charcot–Marie–Tooth disease (CMT2B2)7 and the autosomal recessive neurodevelopmental disorder Microcephaly, seizures, and developmental delay (MCSZ)5,8–12.