INTRODUCTION: Deficiency of IgG (one or more IgG subclases) it’s defined as a level >2 SD below with normal IgG total concentration. It is clinically relevant when is associated with recurrent upper and/or lower respiratory tract infection and/or Ab response defect. Deficiency-IgG3 is the most common.
CASE: 50-year-old man with history of recurrent sinopulmonary infections, tonsillectomy, prolonged use of antibiotics; approach: CD4 lymphocyte subpopulation-29% (692), CD8-21% (504), immunoglobulins IgG-774, IgA-103, IgM-157, IgE-56, IgG-subclasses: IgG1-658 (280-800) , IgG2-235 (115-570), IgG3-9.3 (24-120), IgG4-19.9 (5-125). Diagnosis of autoimmune thyroiditis with secondary treatment of hypothyroidism (levothyroxine) and severe-asthma in step 4 (GINA).
DISCUSSION: IgG3-deficiency is frequent in adults with recurrent respiratory infections caused by Moraxella-sp., and skin infections (erysipelas) caused by S. pyogenes; as an isolated phenomenon it has a critical role against HIV, Dengue, Neisseria and Plasmodium. There is an association with IgA-deficiency, complement-deficiency (lectins) and potential evolution to CVID.
In the IgG subclass deficiencies, treatment is controversial. In the event of severe recurrent infections, prophylactic antibiotics are the first line of treatment and in some cases the substitution with human-immunoglobulin has been discussed.
In this case: an adult with isolated IgG3-deficiency with recurrent-infections, bronchiectasis, autoimmune pathology and severe-asthma due to exacerbations secondary to sinopulmonary-infections required initiation of replacement with IV immune globuline and antibiotic-prophylactic.
CONCLUSION: IgG3 deficiency should not be neglected as a cause of recurrent infections, it can be a marker of minor deficiencies or associated with autoimmune diseases. Treatment with prophylactic antibiotics and IV immune globuline should be individualized according to infections, recurrence, severity, and complications.