These hopes are especially fostered now that adeno-associated virus gene therapy introduced in human muscle has proven both safe and useful for the treatment of lipoprotein lipase (LPL) deficiency (Mingozzi et al., 2009) and thus introduction of specific ankyrin repeat containing proteins into patients is certainly technically and ethically feasible. Here, LPL is linked to hyperinsulinemic hypoglycemia, familial, 4.