When analyzing the underlying IEI in the subgroup of patients suffering from COVID-19 pneumonia, we saw that two had a combined immunodeficiency (P1: MHCII-deficiency; P4: PGM3-deficiency), a form of IEI that has been reported as a risk factor for severe COVID- (24, 25, 27, 58). The gene discussed is PGM3; the disease is hyperinsulinemic hypoglycemia, familial, 4.