IKZF1 and hyperinsulinemic hypoglycemia, familial, 4: However, we found one patient (patient 8.1) with IKAROS deficiency in our cohort developed rheumatoid arthritis 33 years after hypogammaglobulinemia onset, suggesting additional mechanisms, such as impaired T-cell function as described in mouse models, in addition to impaired B-cell function (26–28).