A 2-month-old child is admitted to the ICU with fever, hypotension, tachycardia, and lethargy. The medical history is notable for a similar hospitalization at 2 weeks of age. Physical examination is notable for a temperature of 102°F, oral thrush and rales in the right lung fields. Chest x-ray film reveals multilobular pneumonia. Given the history of recurrent severe infection, the pediatrician suspects an immunodeficiency disorder.

Explain the terms tachycardia, rales, and multilobular pneumonia.
What is the most likely immunodeficiency in this child? Why?
What is an underlying biochemical (genetic) defect in this patient?
Explain why this defect leads to the disease phenotype?
Explain the cellular defects associated with this disease?
What is the overall prognosis for patients with this disorder?