LAUSR

To the Editor, Mendelian susceptibility to mycobacterial disease (MSMD) refers to a group of primary immunodeficiency disorders (PIDs) that characteristically cause susceptibility to mycobacterial infections by a range of mycobacteria and to systemic nontyphoidal salmonellosis [1, 2]. MSMD sufferers are also vulnerable to the more pathogenic Mycobacterium tuberculosis (TB) [3]. To date, the disruption of IFN-γ immunity has been reported in all genetic etiologies of MSMD [2, 4, 5]. The prevalence of MSMD is currently unknown in South Africa and is almost certainly masked by the enormous TB/HIV epidemic [1, 6]. Poor awareness of PID adds to the lack of or late diagnosis. Age of onset of MSMD reported from regions of lower prevalence of TB is typically in infancy with disseminated infection by weakly virulent mycobacteria such as Bacillus Calmette– Guérin (BCG) or atypical mycobacterial species. MSMD clinical presentation and the virulence of the infecting organism in highly endemic regions have only rarely been reported on [2, 7].