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.