PNKP and microcephaly: Microcephaly, seizures, and developmental delay (MCSZ, Online Mendelian Inheritance in Man #613402) is an autosomal recessive disorder associated with mutations in the polynucleotide kinase 3’-phosphatase (PNKP) gene.[1,2] This rare neurodevelopmental condition presents with microcephaly, seizures, and varying degrees of psychomotor developmental delay, often resulting in severe complications or mortality.