This may initially seem problematic given the genetic bases of many immunodeficiencies. But remember that immunodeficiencies aren’t simply genetic disorders; they appear due to a set of poorly understood interactions between the environment and underlying genetic predispositions. It’s not unusual to find adults, even those in the geriatric age range, who develop clinically relevant primary immunodeficiencies, such as common variable immunodeficiency (CVID). Another way of thinking about it is that the immune system is constantly evolving and changing to deal with newer threats, even as we progress through adulthood. If our immune systems cannot keep up with such changes, an immunodeficiency may result.
Moreover, primary immunodeficiencies are only one category. Secondary immunodeficiencies due to medications, malignancies or aging are not uncommon either. Many popular medications, such as certain anticonvulsants, may lead to potentially reversible antibody deficiencies. It’s unreasonable to assume a rheumatologist without additional training can identify a secondary immunodeficiency alone, but referral to a clinical immunologist with expertise certainly can help.
Misconception #3
Autoimmunity is incompatible with immunodeficiency.
It seems counterintuitive that an underactive immune system may lead to autoimmune manifestations. But this is a gross simplification of how our bodies work. The immune system is extraordinarily intricate and when one facet of the immune system does not work properly, it may very well trigger another facet to overcompensate.3 A classic example is early classical complement pathway deficiencies, which can trigger systemic lupus erythematosus (SLE) and SLE-like diseases.
In fact, from the clinical immunologist’s point of view, all autoimmune rheumatologic disease is on the same continuum as immunodeficiency. Unchecked and indiscriminate inflammation may predispose to recurrent or severe infections and other manifestations of immune deficiency. Some clinical data suggest that for a subset of patients with severe, uncontrolled rheumatoid arthritis, immunomodulatory treatment may, on balance, actually reduce the risk of recurrent infections.4
Misconception #4
Immunodeficiency is a laboratory diagnosis.
As a clinical immunologist, this bugs me the most. Many labs can be ordered to assess the integrity of the immune system. But these are only a means to supplement clinical suspicions. Many patients in my clinic don’t have laboratory abnormalities but clearly have otherwise unexplainable immune problems, for which I provide treatment as best as I can. On the other side of the spectrum, I often see patients whose referring providers have identified laboratory abnormalities but have no clinical manifestations concerning for immunodeficiency.
