Mendelian Susceptibility to Mycobacterial Disease: IFN-γ–Driven Immunity Collapse
GIST (Key Takeaways)
- Mendelian susceptibility to mycobacterial disease (MSMD) is a rare inborn error of immunity characterized by heightened susceptibility to low-virulence non-tuberculous mycobacteria. Despite the widespread application of next-generation sequencing, the molecular etiology of approximately 50% of patients remains elusive.
- To date, 22 genes have been implicated, all converging on the IL-12/23–IFN-γ circuit, underscoring its non-redundant role in controlling intracellular pathogens. Isolated MSMD is characterized by a selective predisposition to one or more mycobacterial and related infections.
- But syndromic MSMD’s clinical phenotypes are highly heterogeneous; apart from mycobacterial infections, patients may suffer from viral, bacterial, or fungal diseases, and can additionally manifest auto-inflammation, malignancy, or cutaneous involvement. Current MSMD management mainly hinges on prolonged antimicrobial therapy or align with recombinant human interferon-γ (rhIFN-γ), although allogeneic hematopoietic stem cell transplantation (HSCT) remains the sole curative yet high-risk option; gene editing is still experimental.
- Priorities are early high-risk identification, targeted intervention and full-process management.
Clinical Editorial
Scope and central message
Mendelian susceptibility to mycobacterial disease (MSMD) is described as a rare monogenic immunodeficiency in which impaired interferon-γ (IFN-γ)–mediated immunity permits infections by low-virulence mycobacteria.
The review emphasizes that defects converge on the IL-12/23–IFN-γ pathway, highlighting its essential, non-redundant role against intracellular pathogens.
Genetic landscape and diagnostic gap
Twenty-two genes have been associated with MSMD to date.
Despite broad use of next-generation sequencing, roughly half of affected individuals lack a defined molecular diagnosis in existing studies.
Phenotypic spectrum
Isolated MSMD presents with selective vulnerability to one or more mycobacterial or related infections.
Syndromic forms exhibit marked heterogeneity, with additional susceptibility to viral, bacterial, or fungal infections and extra-infectious manifestations including autoinflammation, malignancy, and skin involvement.
Current management approaches
Therapy primarily comprises prolonged antimicrobial regimens and, in some cases, recombinant human IFN-γ.
Allogeneic hematopoietic stem cell transplantation is noted as the only established curative option but carries substantial risk.
Gene-editing interventions remain experimental.
Operational priorities and limitations
The source prioritizes early identification of high-risk patients, tailored interventions, and comprehensive care pathways.