Obstructive Cholestasis in IL12RB1 Deficiency: A Case Report of an Unusual Hepatobiliary Presentation in Mendelian Susceptibility to Mycobacterial Disease.

While IL12RB1 deficiency is classically associated with susceptibility to mycobacterial and Salmonella infections, its clinical spectrum may be broader than currently documented literature. Timely recognition of atypical pleiotropic presentations can contribute to earlier diagnosis, more tailored interventions, and eventually better patient outcome. However, current literature lacks reports of hepatic involvement such as biliary strictures or intrahepatic cholestasis in IL12RB1-deficient patients. This case exemplifies the diagnostic odyssey of a child with a rare genetic anomaly manifesting as two seemingly unrelated pathophysiologies; the diagnosis was established through genetic testing after exhaustive evaluation excluded infectious, metabolic, and autoimmune etiologies. This case raises the possibility of atypical hepatobiliary manifestations associated with IL12RB1 deficiency. Early genetic testing should be integrated into the diagnostic pathways with undiagnosed cholestasis, and clinicians should remain vigilant for systemic manifestations beyond the classical infectious profile.