CASK and hereditary optic atrophy: Although broad mutation spectrum of the CASK gene, the phenotype shows facial dysmorphism, microcephaly (especially < -3 SD occipitofrontal circumference), hearing impairment, optic atrophy, retinopathy, hypohidrosis, developmental delay, limb hypertonia, pronounced cerebellar hypoplasia, diverse degrees of pons hypoplasia, and a normal-sized corpus callosum [7].