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BACKGROUND

If diagnosed in a timely fashion and monitored adequately, patients with primary immunodeficiency diseases (PIs) infrequently require hospitalization for treatment of infections, flares of autoimmunity, and rarely, management of cancer. The greatest challenge is making an expeditious diagnosis of a PI. Initial evaluation often occurs during a hospitalization for prolonged, severe, or recurrent infections. Occasionally, illnesses due to unusual pathogens raise suspicion for an underlying immunodeficiency. Thus increased awareness of the key features of PIs not only assists in management of these children when admitted, but also helps the pediatric hospitalist identify children at risk for PI. In most cases, these children benefit when the hospitalist can promptly initiate appropriate laboratory studies and obtain consultation from a pediatric immunologist.

CLINICAL PRESENTATION

HISTORY

Prompt identification of children with a PI is paramount to reduce the risk of irrevocable sequelae of invasive infections, such as bronchiectasis, encephalitis, or kidney failure. Establishing a set of clear warning signs that indicate a PI has been challenging because of the subjective nature of what constitutes a “severe” infection or exactly what pattern constitutes “recurrent” infections. To address this concern, the Jeffrey Modell Foundation worked with experts on a list of 10 warning signs (Table 49-1), the presence of two or more of which should raise suspicion of PI. Of note, these warning signs largely emphasize infections as a core feature of PI. Two recent analyses found these 10 warning signs fail to identify many subjects with PIs.1,2 Missing from this list are features of defective tolerance, including autoimmune and allergic diseases, and malignancies. Furthermore, the need for intravenous antibiotics, failure to thrive, or a relevant family history were recently found to be the strongest predictors of PI.3,4

TABLE 49-1The Jeffrey Modell Foundation’s 10 Warning Signs of Primary Immunodeficiency

To address the complexity of evaluating the suspicion for PI, multi-step flow charts have been developed to facilitate early identification by screening patients based on history and physical examination.5,6

A recent success in the early detection of patients with severe PI was the development of a qPCR-based assay that gauges post-thymic T-cells, which identifies newborns with T-cell lymphopenia such as in severe combined ...

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