CD40LG and hyperinsulinemic hypoglycemia, familial, 4: Boys with CD40 ligand deficiency suffer an excess risk of malignant disease affecting the biliary tree (Hayward et al, 1997; Levy et al, 1997) and intestine, including neuroendocrine tumours (Zirkin et al, 1996; Malhotra & Li, 2008).