Acquired IgG subclass deficiency is both a pediatric and adult concern. Accurate diagnosis can be complex because of variability in measurement techniques and interpretation of antibody-forming capacity.

A 49-year old Caucasian male in excellent previous health presented with complaints of recurrent infections of the ear, skin, and prostate. The patient had been treated with multiple courses of antibiotics. A 6-year old African-American female presented with recurrent infections of the ear, sinuses, lungs, and throat. The patient was full-term and healthy up until 8 months of age, with normal IgG and subclasses obtained at age 3 years.

Besides routine labs, IgG, IgA, IgM and IgG subclasses were obtained. Pre-pneumococcal antibodies were assessed followed by vaccination with post-pneumococcal antibody titers drawn at 2 and 4 weeks.

The adult's immunodeficiency revealed normal IgA and IgG, low IgM and IgG-3 subclass deficiency. The child had a low IgA, total IgG level at the low end of normal with IgG-1 subclass deficiency. Both patients had defective antibody responses to the pneumococcal vaccine in all the strains of bacteria.

The diagnosis of a IgG subclass deficiency should be considered in both children and adults with recurrent infections. IgG subclass deficiency may still be a possibility even when the total IgG is normal. A detailed history of infections and antibody-forming capacity is recommended. IVIG is recommended for treatment of the condition.