The highly variable prognosis of this disease may be predicted using a number of biomarkers, including CD38 expression level.[1] Human CD38 is a transmembrane glycoprotein that catalyzes the synthesis of cyclic ADP ribose (cADPR), an important second messenger mobilizing Ca2+ from Ryanodine-sensitive intracellular stores.[2,3] CD38 has also the ability to mediate cell-cell interactions by binding the non-substrate ligand CD31 (PECAM-1, a member of the Ig superfamily), which is expressed on endothelial cells, nurse-like cells, and CLL cells. The gene discussed is PECAM1; the disease is B-cell chronic lymphocytic leukemia.