Molecular studies for cryptosporidium infection, involving polymerase chain reaction amplication of parasite DNA in patients with CD40 ligand deficiency suggest that subclinical infection is common and in many cases the organism is not detectable by stool microscopy, but only by molecular testing (McLauchlin et al, 2003). This evidence concerns the gene CD40LG and hyperinsulinemic hypoglycemia, familial, 4.