T lymphocytes andnatural killer cells of affected patients express a defective IL-12 receptor on theircell surfaces, leading to low production of IFN-γ, which is the major factor responsiblefor mycobacterial death.(13) The diagnosis of IFN-γ/IL-12 pathway defects requires a tiered approach andlaboratory support.(14) In patients with severe disseminated mycobacterial infection, otherimmunodeficiency disorders, such as severe combined immunodeficiency, should be excludedfirst. Here, IFNG is linked to immunodeficiency disease.