Leukocytoclastic Vasculitis in IL-12RB1 deficiency: a rare manifestation of Mendelian susceptibility to mycobacterial disease.

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare genetic condition caused by mutations in the interleukin-12/interferon-gamma pathway, leading to vulnerability to infection by weakly virulent mycobacteria. IL-12Rβ1 deficiency, the most common cause of MSMD, has rarely been associated with cutaneous leukocytoclastic vasculitis (LCV). We report the case of a 9-year-old girl with IL-12Rβ1 deficiency who presented with recurrent maculopapular skin lesions confirmed as LCV on biopsy. The patient's clinical course included disseminated BCGitis, a history of kidney anomalies, and periodic erythematous rashes exacerbated by physical pressure. Laboratory findings revealed elevated inflammatory markers and immune dysregulation, and a skin biopsy confirmed leukocytoclastic vasculitis. Treatment with topical corticosteroids and antihistamines resulted in clinical improvement. This case highlights the importance of recognizing LCV as a potential manifestation of IL-12Rβ1 deficiency and underscores the need for a multidisciplinary approach in managing these patients.