In humans, patients with X‐linked lymphoproliferative disease type II (XLP‐2) lack functional XIAP but show normal blood cell counts under conditions of health (Rigaud et al, 2006) and even lymphoproliferation upon infection (Filipovich et al, 2010; Pachlopnik Schmid et al, 2011). Here, XIAP is linked to X-linked lymphoproliferative disease.