46 year-old female RN started having recurrent furuncle/abscess on almost her entire body approximately 4 weeks after her first baby was born 15 years ago. In her infectious disease physician’s mind, these are “the worst skin infections” he has seen. They required multiple incision and drainage with numerous courses of oral and intravenous antibiotics. A few cultures from the wound showed MRSA. In addition, she also reports 4 cases of pneumonia in her life. This first one happened after she had her first baby for which she was hospitalized for 3 weeks.
Finally, 3 years ago, she was referred to an allergist and was diagnosed with PID - selective IgG deficiency. She was put on monthly IVIG. Since then, she has experienced “significant” improvement of her skin infection. This means a reduction in the frequency of recurrence, reduction of number of boils from each flare-up and severity of each boil. She also reports there is no need for intravenous antibiotics for each flare as oral antibiotic seems to be working. She reports no more “Pneumonia” while she was on monthly IVIG. She has never had frequent OM, sinusitis, or bronchitis. She denied joint pain, swelling, or stiffness. She was diagnosed with Hashimoto thyroiditis 10 years ago and then she was told she had a goiter for which she had a thyroidectomy in 2005. She denied chronic diarrhea.
Now she is concerned that she may have “side effects” from IVIG Gammagard as she always develops a headache the same night IVIG is given, which usually lasts about 3-4 days then disappears on its own. She also feels “drained” with tiredness for a few days after IVIG. All her available labs were reviewed. The only low immunoglobulin are IgG2 at 187 (241-700 mg/dl) and IgG3 at 15 (22-178 mg/dl) (an example from Oct., 2010). Her repeat lab in May, 2013 shows only Ig3 is low at 18 (22-178). All others are normal except streptococcus pneumonia shows 7/14 (50% >2.0 mcg/ml) serotype are protective against invasive pneumococcal disease. My questions are:
1. I don’t think the low IgG2 and IgG3 can explain her skin infections – recurrent MRSA furunculosis; do you agree?
2. Did we miss anything in her case for diagnosis? Should we perform more tests for innate immune disorder? I think her cellular immune function is good.
3. If the replacement of immunoglobulin is medically necessary, will it be better to switch her to subcutaneous injection?
4. If the replacement of immunoglobulin is continued, how should we monitor her? Her persistent low Ig3 despite IVIG indicates a need for increasing her current dosage?