Transient Hypogammaglobulinemia of Infancy By James Fernandez, MD, PhD, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University Reviewed / Revised Jan 2023 View Patient Education Transient hypogammaglobulinemia of infancy is a temporary decrease in serum IgG and sometimes IgA and other immunoglobulin (Ig) isotypes to levels below age-appropriate normal values.