Homozygous Intragenic Deletion in WDR62 in Siblings with Primary Microcephaly

Introduction: Primary microcephaly is genetically heterogeneous. Despite the rapid evolution of scientific information and bioinformatic tools, etiology remains elusive in more than half of the affected population. A substantial fraction of these undiagnosed cases is anticipated to have large structural variations in one of the causative genes. This class of variations has been difficult to detect by exome sequencing. Case Presentation: We report a sibling pair with global developmental delay, microcephaly, and brain abnormalities who were recruited under the Indian Undiagnosed Disease Program (I-UDP) for further evaluation after an uninformative initial exome sequencing. Conclusion: Copy number analysis using whole genome sequencing data detected a large homozygous deletion of 9.78 kb encompassing exon 1 to exon 3 of WDR62 (OMIM*613583). These results were further validated by performing comparative quantification of the copy number of deleted exons in both siblings and parents.