IGHG3 and hyperinsulinemic hypoglycemia, familial, 4: While these carriers are certainly not severely immunodeficient (because the allele is common), it is well known that various types of limited Ig deficiency (for example, IgG2 and IgG3 subclass deficiency) confer an increased incidence of infections, including with Neisseria meningitidis and other meningitis pathogens.