Similar to γc chain-deficient X-linked SCID, deficiency of JAK3 is known to cause autosomal recessive SCID with a reduced number of T-cells and natural killer cells as well as dysfunctional B-cells in normal cell count (T−B+NK− SCID) and hypogammaglobulinemia [42]. Here, JAK3 is linked to T-B+ severe combined immunodeficiency due to gamma chain deficiency.