IFNG and severe combined immunodeficiency: Investigations for severe combined immunodeficiency (SCID), human immunodeficiency virus (HIV) and chronic granulomatous disease (CGD) were negative; evaluation of peripheral blood mononuclear cell cytokine production showed normal production of IL-17 and IL-12, but reduced production of IFN-gamma following polyclonal stimuli, suggesting a potential defect in macrophage/T-cell signalling; he subsequently started subcutaneous interferon-gamma therapy.