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USMLE (United States Medical Licensing Examination) Practice Exam 08

Practice exam for USMLE (United States Medical Licensing Examination).

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Question 1 of 1000%

Time remaining120:00

Attempts allowedUnlimited

Difficulty mixE • M • H

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Question 1

MEDIUM

120:00

A 9-month-old boy has recurrent infections with catalase-positive organisms and granuloma formation. Neutrophils show absent fluorescence on dihydrorhodamine (DHR) flow cytometry testing. Which of the following best explains the underlying defect?

Absent DHR fluorescence indicates impaired oxidative burst due to NADPH oxidase deficiency, consistent with chronic granulomatous disease and susceptibility to catalase-positive organisms.

Select one answer

Defective NADPH oxidase leading to decreased respiratory burst

Defective myeloperoxidase leading to impaired hypochlorous acid formation

Defective C1 esterase inhibitor leading to increased bradykinin

Defective IL-12 receptor leading to impaired Th1 differentiation

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USMLE (United States Medical Licensing Examination) Practice Exam 08

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