The first patient with sporadic X-linked intellectual disability with de novo ZDHHC9 mutation identified by targeted next-generation sequencing

X-linked intellectual disability (XLID) is a genetically heterogeneous disorder involving more than 100 genes known to date. Here, we describe a Korean male infant with global developmental delay. He had neither facial dysmorphism nor skeletal abnormalities. Bayley scale of infant and toddler development third edition (Bayley-III) measured at age of 2 years revealed marked global developmental delays without Marfanoid habitus, structural brain abnormalities, or epilepsy. The patient's cognitive, motor, and language developmental ages were 8-9 months, 12 months, and 9 months, respectively. Targeted next-generation sequencing revealed a de novo mutation [NM_001008222.2(ZDHHC9): c.286C > T (p.(Arg96Trp))] in the affected patient. This mutation has been reported previously in a family XLID with Marfanoid features. Sanger sequencing analysis of the proband and his parents revealed that the missense mutation was present in the proband only (absent in his parents). This indicates that the mutation is de novo in origin. To the best of our knowledge, this is the first report describing sporadic XLID with de novo ZDHHC9 mutation identified by targeted next-generation sequencing.