Diagnostic Approach to the Adult with Suspected Immune Deficiency

Primary and secondary immunodeficiency disorders are a diverse group of illnesses resulting from one or more abnormalities of the immune system. The clinical manifestations include increased susceptibility to infection and an increased risk for autoimmune disease and malignancy. Primary immune deficiency (PID) diseases are a group of serious disorders arising from an intrinsic defect in the immune system, generally the result of a genetic disease that can be traced directly to a particular immune pathway. In contrast, secondary immune deficiencies stem from impairment of the immune response through another mechanism, such as an infection, metabolic derangement, malignancy or toxins, with the immune defect being a secondary manifestation. Although the possibility of immunodeficiency should be considered in any individual with recurrent infections, it is also important to consider nonimmune conditions as a cause. Such disorders include circulatory abnormalities leading to stasis or cellular ischemia, as can occur in sickle cell disease, diabetes or heart failure; obstructive lung conditions such as chronic obstructive pulmonary disease, ciliary dyskinesia, and cystic fibrosis; or ureteral stenosis, resulting in defective pathogen clearance; and breaches in the integument and mucosal surfaces, as is seen in erythema multiforme or burns, allowing entry to opportunistic organisms and infection. Each of these is associated with infection by specific pathogens and results in characteristic clinical manifestations.