SH2D1A and X-linked lymphoproliferative syndrome: Loss of SAP unveils the full inhibitory potential of SLAM receptors, causing X-linked lymphoproliferative disease type 1 (XLP-1, Duncan disease), a primary immunodeficiency characterized by perturbed TCR signaling and several hematological alterations, such as dysgammaglobulinemia, EBV-triggered hemophagocytic lymphohistiocytosis, and lymphomas [90].