Evaluation of Suspected Immunodeficiency

Primary care physicians must have a high index of suspicion to diagnose immune system defects early enough to institute appropriate treatment before irreversible damage develops. Diagnosis can be difficult because most affected patients do not have abnormal physical features. The most typical manifestation of immunodeficiency in children is recurrent sinopulmonary infections. Although infections are common in children in general, an infection exceeding the expected frequency and usually involving multiple sites can suggest immunodeficiency. A single, severe, opportunistic, or unusual infection can also be the presentation of an immunodeficiency ( Table 148.1 ). Increasingly recognized is the co-occurrence of autoimmune disease or inflammatory conditions and recurrent infections. Newborn screening for T-cell lymphopenia has been instituted in most states; this has led to the identification of some infants with immunodeficiency before any clear manifestations but is limited to T-cell deficiencies. Additional clues to immunodeficiency include failure to thrive with or without chronic diarrhea, persistent infections after receiving live vaccines, and chronic oral or cutaneous candidiasis ( Tables 148.2 and 148.3 ).