A global registry of patients with genetic defects in the IL-12/IL-23/IFN-γ axis such as that available at www.lovd.nl/IL12RB1 for IL-12Rβ1 defects, and that are also available for most other genes that cause MSMD, together with awareness of these immunodeficiencies prior to BCG vaccination will improve the health and quality of care for these patients. Here, IFNG is linked to Mendelian susceptibility to mycobacterial diseases.