Immunology USMLE Step 1 Practice Question
A 4 month old boy is hospitalized for persistent thrush, chronic diarrhea, and Pneumocystis jirovecii pneumonia. He has had poor weight gain since birth. Flow cytometry shows markedly decreased T cells and B cells, and chest radiograph shows an absent thymic shadow. Which of the following mechanisms most likely explains this disorder in this patient?
Answer choices
- ATerminal complement deficiency causing impaired membrane attack complex formation
- BDeficiency of adenosine deaminase leading to toxic buildup of deoxyadenosineCorrect answer
- CLack of CD18 integrin preventing neutrophil adhesion
- DMutation in gp91phox causing absent respiratory burst
- EFailure of phagolysosome formation in neutrophils
- FDeficiency of purine nucleoside phosphorylase leading to accumulation of deoxyguanosine
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