Since the identification of the first genetic etiology of this syndrome in 1996, nine morbid genes (IFNGR1, IFNGR2, IRF8, STAT1, CYBB, NEMO, IL12B, IL12RB1 and ISG15) and 17 different genetic etiologies of MSMD have been discovered. The gene discussed is ISG15; the disease is Mendelian susceptibility to mycobacterial diseases.