IL12B Deficiency is a rare condition involving the immune system characterized by an impairment of interferon-gamma mediated immunity. This condition is typified by susceptibility to mycobacterial species, such as Mycobacterium tuberculosis, environmental non-tuberculous mycobacteria and the Bacillus Calmette-Guerin (BCG) vaccine. Thus, patients present with BCG disease after routine vaccination in childhood. In addition, affected patients may also be susceptible to Salmonella infections.
The clinical severity of the immunodeficiencies involving interferon gamma varies widely, and depends on the degree of impairment of interferon-gamma mediated immunity. In the most severe of cases, patients develop lepromatous-like lesions in early childhood, and ultimately succumb to mycobacterial infections. In relatively milder cases, patients develop disseminated but curable infections with tuberculoid granulomas later on in their life. Most cases of IMD29 are of the mild form, and prognosis is generally good. Diagnosis is made on the basis of clinical features and by the absence of detection of IL12B secretion from leukocytes. Extended periods of therapy with antimycobacterial drugs may be required for those patients who are infected, along with recombinant IFN gamma. BCG immunization is contraindicated, and other live vaccines should also be avoided.