The severity of the clinical phenotype of MSMD depends on the genotype. Complete IFN-γR1 or R2 deficiencies lead to the abrogation of responses to IFN-γ. Such patients presents in early childhood with disseminated NTM or BCG infections, resulting in a high mortality, despite chemotherapy. Mycobacterial lesions in such patients are multibacillary and associated with poor granuloma formation. In contrast, partial IFN-γR1 deficiency, complete IL-12B deficiency, and IL-12/23 receptor deficiency predispose to mycobacterial infections, presenting at a later age and with a favorable outcome, following chemotherapy. Lesion in these latter patients are paucibacillary and are associated with an intact granulomatous response.