EIF2AK3 and hyperinsulinemic hypoglycemia, familial, 4: Perk deficiency in humans is the cause of the Wolcott-Rallison Syndrome characterized by permanent neonatal diabetes, exocrine pancreas deficiency, osteopenia, and growth retardation [9] and these defects are recapitulated in Perk KO mice [10], [11], [12].