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free120/Block 2/Question#17 (11.9 difficulty score)
A 6-year-old girl is admitted to the hospital ...

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submitted by itsalwayslupus(27),

From Pathoma Ch. 2 pg. 14: MPO deficiency results in defective conversion of H2O2 to HOCl. Increased risk for Candida infxns (although most patients asymptomatic). Nitroblue tetrazolium test is normal because the respiratory burst is actually still intact. This patient has candida infection and delayed, but still can kill staph a, which seemingly goes along with the fact that the respiratory burst is still intact, but without MPO it may be hindered a little.

Why not superoxide dismutase? Its the step right in between NADPH (chronic granulomatous disease) and MPO

ilikedmyfirstusername  I guess that could potentially manifest as an even worse phenotype in SCID? +  
thekneesofbees  Its because SOD forms H2O2, but H2O2 is broken down by catalase. Since Staph Aureus is catalase positive, it wouldn't be killed by it anyway. +2