Mutations in these genes may be responsible for TB in other children, particularly if the morbid alleles concerned display incomplete penetrance for the case-definition phenotype of MSMD, such as IL12B and IL12RB1. Mutations in other genes possibly but not necessarily related to IFN-γ-mediated immunity, may also be involved. The gene discussed is IL12B; the disease is Mendelian susceptibility to mycobacterial diseases.