ADA and severe combined immunodeficiency: The classical example is severe combined immunodeficiency (SCID) with defects in T cells, B cells, and NK cells caused by defects in IL2RG, RAG1/2, ADA, JAK3, and IL7R genes, in which an increased risk of disseminated VZV infection has been well-recognized for many years (Arvin et al. 2010; Carter-Timofte et al. 2018b; Fischer et al. 2015; Zerboni et al. 2014).