Mendelian Susceptibility To Mycobacterial Diseases

Mendelian susceptibility to mycobacterial diseases (MSMD) is a rare immunodeficiency syndrome, with susceptibility to mycobacteria, such as the vaccine against tuberculosis (bacillus Calmette-Guérin (BCG) and environmental mycobacteria. It is characterized by severe, recurrent infections, either systemic (widespread) or localized. It has many subtypes. The most serious types are the autosomal recessive complete interferon gamma receptor 1 (IFN-gammaR1) and receptor 2 (IFN-gammaR2) deficiencies. MSMD due to partial IFN-gammaR1, partial IFN-gammaR2, complete IL-12R-beta1, complete IL12B, complete ISG15, partial STAT1 and partial IRF8 deficiencies and MSMD due to partial X-linked recessive (XR) mutations are less severe subtypes. Only about half of patients with MSMD have an identified genetic cause. Nine genes are known to be responsible for MSMD. Seven of them are inherited in an autosomal recessive or autosomal dominant pattern (IFNGR1, IFNGR2, STAT1, IL12B, IL12RB1, IRF8 and ISG15 genes) and 2 are X-linked (IKBKG and CYBB genes). BCG vaccination should be avoided in those with MSMD. Treatment includes antibiotics and surgery for lymph node removal in some cases. Hematopoietic stem cell transplantation (HSCT) may be considered in specific cases. Prognosis depends on the specific mutation and the associated disorder.