Pre-T cell receptor-α immunodeficiency detected exclusively using whole genome sequencing.

Maturation of αβ lineage T cells in the thymus relies on the formation and cell surface expression of a pre-T cell receptor (TCR) complex, composed of TCRβ chain and pre-TCRα (pTCRα) chain heterodimers, giving rise to a diverse T cell repertoire. Genetic aberrations in key molecules involved in T cell development lead to profound T cell immunodeficiency. Definitive genetic diagnosis guides treatment choices and counseling. In this study, we describe the role of whole genome sequencing (WGS) in providing a definitive diagnosis for a child with T cell deficiency, where targeted panel sequencing of SCID genes and whole exome sequencing had failed. A novel homozygous 8kb deletion in PTCRA, encoding pTCRα, was identified. To date, use of WGS remains restricted and for many geographical regions, is clinically unavailable.