Mice lacking Casp8 in T cells develop RIPK1-driven lymphoproliferative syndromes (Ch’en et al, 2011, 2008; Salmena and Hakem, 2005), whereas we demonstrate that the absence of Ripk1 induces caspase-8-driven lymphopenia and intestinal malignancies. The gene discussed is RIPK1; the disease is lymphopenia.