The KIF1A p.T99M variant identified in P174 is a recurrent de novo variant previously reported in a number of individuals with thin corpus callosum, cerebellar atrophy and a progressive clinical course involving microcephaly, severe global developmental delay, ID, cortical visual impairment, hypotonia, hyperreflexia and variable features including optic atrophy, spastic paraparesis and seizures.26–28 P781 had mixed spastic/dystonic diplegic CP with intermittent hypertonicity, microcephaly, developmental delay and cortical visual impairment. Here, KIF1A is linked to hereditary optic atrophy.