Myeloperoxidase (MOP) is present in monocyte and neutrophil lysosomes, catalyzing hydrogen peroxide and chloride ion conversion to hypochlorous acid. MOP seems to destroy pathogens during phagocytosis by neutrophils and is considered an important defense against innumerous bacteria. We present a patient who had MOP deficiency, who presented with a subacute form of paracoccidioidomycosis and later with peritoneal tuberculosis. MOP deficiency leads to the diminished destruction of phagocytized pathogens. This case gives important evidence of an association between MOP deficiency and increased susceptibility to infection by Paracoccidioides brasiliensis and Mycobacterium tuberculosis.