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Homozygous Duplication Identified by Whole Genome Sequencing Causes LRBA Deficiency

In more than one third of primary immunodeficiency (PID) patients, extensive genetic analysis including whole exome sequencing (WES) fails to identify the genetic defect. Whole genome sequencing (WGS) is able to detect variants missed by other genomics platforms, enabling the molecular diagnosis of otherwise unresolved cases. Here, we report two siblings, offspring of consanguineous parents, who experienced similar severe events encompassing early onset of colitis, lymphoproliferation and hypogammaglobulinemia, typical of lipopolysaccharide (LPS)-responsive and beige-like anchor protein (LRBA) or cytotoxic T-lymphocyte-associated protein 4 (CTLA4) deficiencies. WGS of these patients detected a 12.3 kb homozygous tandem duplication that was absent in control cohorts and is predicted to disrupt the reading frame of the LRBA gene.