7 . ▁This ▁dis order ▁is ▁due ▁to ▁a ▁ha p lo ins u ffic iency ▁of ▁the ▁trans cription ▁factor ▁ 4 ▁( T CF 4 ) ▁gene ▁which ▁is ▁located ▁on ▁the ▁long ▁arm ▁of ▁chrom os ome ▁ 1 8 ▁( 1 8 q 2 1 . 2 ) ▁The ▁mut ational ▁spectrum ▁appears ▁to ▁be ▁ 4 0 % ▁point ▁mut ations , ▁ 3 0 % ▁small ▁delet ions / insert ions ▁and ▁ 3 0 % ▁delet ions . ▁All ▁appear ▁to ▁be ▁de ▁nov o ▁mut ations . ▁The ▁risk ▁in ▁sib lings ▁is ▁low , ▁but ▁higher ▁than ▁the ▁general ▁population ▁due ▁to ▁parent al ▁ger ml ine ▁m osa ic ism . ▁ ▁A ▁Pitt – H op kins - like ▁phen ot ype ▁has ▁been ▁assigned ▁to ▁aut os om al ▁re cess ive ▁mut ations ▁of ▁the ▁contact in ▁associated ▁protein ▁like ▁ 2 ▁( CN T N AP 2 ) ▁gene ▁on ▁the ▁long ▁arm ▁of ▁chrom os ome ▁ 7 ▁( 7 q 3 3 - q 3 6 ) ▁and ▁the ▁ne ure x in ▁ 1 ▁alpha ▁( NR X N 1 ) ▁gene ▁on ▁the ▁short ▁arm ▁of ▁chrom os ome ▁ 2 ▁( 2 p 1 6 . 3 ). ▁ ▁Mal form ations ▁in ▁the ▁C NS ▁can ▁be ▁seen ▁in ▁about ▁ 6 0 ▁to ▁ 7 0 % ▁of ▁patients ▁on ▁M RI ▁sc ans . ▁ ▁Pitt – H op kins ▁patients