Suspected Mendelian Susceptibility to Mycobacterial Disease (MSMD): A Case Series

Introduction: MSMD is caused by congenital errors in the immunity of the IL-12/IFN-γ axis, the main pathway for immunity against intramacrophage pathogens.
Case 1: Male, 62-year-old, no reported consanguinity or endogamy, a history of deaths in children under 5 years, no BCG scar. History of congenital heart disease with valve replacement due to aortic stenosis, on Warfarin treatment, bacterial meningitis in 2008 attributed to a dental procedure complication with subsequent focal epilepsy and bilateral hearing loss, no need for antifimic treatment. In September 2022, clinical signs and lumbar puncture findings suggestive of tuberculous meningitis, positive geneXpert for mycobacteria managed with DOTBAL, normal immunoglobulins and lymphocyte subpopulations.
Case 2: Female, 32-year-old, no reported consanguinity or endogamy, family history of malignancy and autoimmunity, history of childhood herpes simplex infections. Presented with disseminated lymph node tuberculosis in March 2022, received 3 months of intensive DOTBAL treatment and 9 months of maintenance. Decreased CD3 and CD4, abdominal CT scan revealing retroperitoneal cystic tumors, multiple retroperitoneal lymphadenopathies, and cystic nodules adjacent to the pancreas.
Case 3: Female, 21-year-old, probable consanguinity on maternal side, family history of tuberculosis on paternal side, history of retained deciduous teeth. Diagnosed with lymph node tuberculosis by PCR in 2019 with relapse in 2021. Required intensive DOTBAL treatment and maintenance for 10 months. Positive CMV IgM, normal lymphocyte subpopulations and immunoglobulins.
Discussion: This is a case series involving extrapulmonary mycobacterial infections. Secondary immunodeficiency or severe combined immunodeficiency was ruled out, with a high suspicion of MSMD due to the milder presentation of the disease at the age of onset, except for one patient with documented consanguinity, an earlier age of onset, and infection relapse.
Exome sequencing is necessary to identify genetic defects in these patients. If negative, the possibility of a phenocopy should be considered.

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