X chromosome exome sequencing reveals a novel ALG 13 mutation in a nonsyndromic intellectual disability family with multiple affected male siblings

X‐linked intellectual disability (XLID) is a heterogeneous condition associated with mutations in >100 genes, accounting for over 10% of all cases of intellectual impairment. The majority of XLID cases show nonsyndromic forms (NSXLID), in which intellectual disability is the sole clinically consistent manifestation. Here we performed X chromosome exome (X‐exome) sequencing to identify the causative mutation in an NSXLID family with four affected male siblings and five unaffected female siblings. The X‐exome sequencing at 88× coverage in one affected male sibling revealed a novel missense mutation (p.Tyr1074Cys) in the asparagine‐linked glycosylation 13 homolog ( ALG13 ) gene. Segregation analysis by Sanger sequencing showed that the all affected siblings were hemizygous and the mother was heterozygous for the mutation. Recently, a de novo missense mutation in ALG13 has been reported in a patient with X‐linked congenital disorders of glycosylation type I. Our study reports the first case of NSXLID caused by a mutation in ALG13 involved in protein N ‐glycosylation. © 2013 Wiley Periodicals, Inc.