Leukocytoclastic vasculitis in patients with IL12B or IL12RB1 deficiency: case report and review of the literature.

Background: Mendelian susceptibility to mycobacterial disease (MSMD) is an inborn error of immunity, resulting in susceptibility to weakly virulent mycobacteria and other intramacrophagic pathogens. Rheumatologic manifestations and vasculitis are considered rare manifestations in MSMD patients.

Case Presentation: In this study, we reported a 20-year-old female who was presented with recurrent lymphadenitis following bacillus Calmette-Guérin (BCG) vaccination and a history of recurrent disseminated rash diagnosed as leukocytoclastic vasculitis (LCV). A slight reduction in lymphocyte subsets including CD4+, CD19+, and CD 16 + 56 T-cell count, as well as an elevation in immunoglobulins level (IgG, IgA, IgM, IgE), were observed in the patient. Whole exome sequencing revealed a homozygous Indel-frameshift mutation, c.527_528delCT (p. S176Cfs*12), at the exon 5 of the IL12B gene. She experienced symptom resolution after treatment with anti-mycobacterial agents and subcutaneous IFN-γ. We conducted a manual literature search for MSMD patients reported with vasculitis in PubMed, Web of Science, and Scopus databases. A total of 18 MSMD patients were found to be affected by a variety of vasculitis phenotypes mainly including LCV and Henoch-Schönlein purpura (HSP) with often skin involvement. Patients were all involved with vasculitis at the median age of 6.8 (2.6-7.7) years, nearly 6.1 years after the initial presentations. Sixteen patients (88.9%) had IL12RB1 defects and concurrent Salmonella infection was reported in 15 (88.2%) patients.

Conclusion: The lack of IL-12 and IL-23 signaling/activity/function and salmonella infection may be triggering factors for the development of leukocytoclastic vasculitis. IL12B or IL12RB1 deficiency and salmonellosis should be considered in MSMD patients with vasculitis.