Mondo Description Mendelian susceptibility to mycobacterial diseases (MSMD) due to partial STAT1 (signal transducer and activator of transcription 1) deficiency is a genetic variant of MSMD characterized by a partial defect in the interferon (IFN)-gamma pathway, leading to mild mycobacterial infections.

Uniprot Description A form of Mendelian susceptibility to mycobacterial disease, a rare condition caused by impairment of interferon-gamma mediated immunity. It is characterized by predisposition to illness caused by moderately virulent mycobacterial species, such as Bacillus Calmette-Guerin (BCG) vaccine, environmental non-tuberculous mycobacteria, and by the more virulent Mycobacterium tuberculosis. Other microorganisms rarely cause severe clinical disease in individuals with susceptibility to mycobacterial infections, with the exception of Salmonella which infects less than 50% of these individuals. Clinical outcome severity depends on the degree of impairment of interferon-gamma mediated immunity. Some patients die of overwhelming mycobacterial disease with lepromatous-like lesions in early childhood, whereas others develop, later in life, disseminated but curable infections with tuberculoid granulomas. IMD31A has low penetrance, and affected individuals have relatively mild disease and good prognosis. IMD31A confers a predisposition to mycobacterial infections only, with no increased susceptibility to viral infections.