The Missing Pulse in a Discordant Triad: The Challenge of Biologic Selection in Multisystem Autoimmunity: A Case Report

Introduction Takayasu arteritis is a large-vessel vasculitis that clinicians increasingly encounter in the context of other immune-mediated disorders. Even so, finding it in a patient who already has both inflammatory bowel disease and psoriasis is highly unusual. This report outlines the diagnostic workup and targeted biologic management of this rare overlap. Case Presentation A 36-year-old woman with a known history of chronic plaque psoriasis and ulcerative colitis was admitted for an elective cesarean section. During routine perioperative checks, she was incidentally found to have an absent left radial pulse. A follow-up Computed Tomography (CT) angiogram revealed complete non-opacification of the left subclavian artery and high-grade concentric stenosis of the left common carotid artery, consistent with Type I Takayasu arteritis. Given her complex autoimmune profile, she was started on intravenous infliximab. She responded well across all affected systems. After four doses, her Indian Takayasu Clinical Activity Score dropped to 1, her colitis symptoms cleared, and her skin plaques healed. She continues to remain stable in outpatient follow-up. Conclusion This case highlights the challenges of biologic selection in patients with coexisting immune-mediated diseases affecting multiple organ systems. The favorable response to infliximab in our patient suggests that a single biologic agent may achieve effective control of vascular, intestinal, and cutaneous disease manifestations in complex autoimmune overlap syndromes.