Thank you for your inquiry.
Your young lady has selective IgA deficiency. This is defined as a level of serum IgA less than 0.07 grams per liter with normal serum IgG and IgM levels in a patient older than 4 years without any known cause of IgA deficiency.
The symptoms of selective IgA deficiency can be highly variable and many are asymptomatic. On occasion, such patients can have impaired specific antibody formation to pneumococcal and other vaccines. Such patients also can have an increased incidence of atopic disease, autoimmunity, and other associated conditions.
On the basis of your history, your patient does not exhibit a significant history of recurrent bacterial infections, and at least according to the information you have given, does not have evidence for chronic bacterial infection (chronic sinusitis or bronchiectasis). In addition, she has not experienced any documented bacterial pneumonia. Thus, at least the interpretation of the history that I get from your description is that she has been relatively asymptomatic.
The exact cause of the elevated IgG is unknown in such cases, but theoretically some experts have considered this to be due to a compensatory response in the absence of IgA. We know, for example, that IgM can be elevated in such patients. This previously has been thought to be a compensatory response as well, but occasionally enzyme deficiency such as uracil nucleoside glycosylase can lead to a hyper-IgM response in association with low IgA levels (but in these cases, IgG is usually low as well).
In view of the fact that your patient appears not to have any documentation of chronic bacterial or even acute recurrent bacterial infections (and is relatively healthy), I agree with your strategy of continued observation without therapy. In fact, if there are bacterial complications, antibiotic therapy could be indicated, and immunoglobulin replacement is only rarely used in patients with specific IgA deficiency. For a more detailed discussion of the issue of potential therapies, I refer you to the Practice Parameter for the diagnosis and management of primary immunodeficiency which is available to you without charge online. The first author is Dr. Francisco Bonilla, and the discussion on selective IgA deficiency begins on Page S28.
Thank you again for your inquiry and we hope this response is helpful to you.
Phil Lieberman, M.D.