A neurodevelopmental disorder caused by variation in the KCNK3 gene. This disorder is characterised by global developmental delay, central and/or obstructive sleep apnea. hypotonia, and feeding difficulties. Most patients also present structural malformations, including microcephaly, arthrogryposis/flexion contractures, scoliosis, cleft palate and bilateral talipes, with some facial dysmorphology, and ambiguous genitalia in male probands.