Deletion in Xp22.11: PTCHD1 is a candidate gene for X-linked intellectual disability with or without autism

Submicroscopic chromosomal anomalies play an important role in the aetiology of intellectual disability (ID) and have been shown to account for up to 10% of non-syndromic forms. We present a family with two affected boys compatible with X-linked inheritance of a phenotype of severe neurodevelopmental disorder co-segregating with a deletion in Xp22.11 exclusively containing the PTCHD1 gene. Although the exact function of this gene is unknown to date, the structural overlap of its encoded patched domain-containing protein 1, the transmembrane protein involved in the sonic hedgehog pathway, and its expression in human cortex and cerebellum as well as in mice and drosophila brain suggests a causative role of its nullisomy in the developmental phenotype of our family. Our findings support the recent notions that PTCHD1 may play a role in X-linked intellectual disability (XLID) and autism disorders.