ITPA and hyperinsulinemic hypoglycemia, familial, 4: Indeed, two functional variants (rs1127354 and rs7270101) in the ITPA gene that cause inosine triphosphatase (ITPase) deficiency were shown to protect against RBV-induced hemolytic anemia during the early stages of treatment [21], but these variants showed strong geographical and ethnic differences in allelic frequencies [22].