KILT Syndrome associated with congenital agenesis of the brachiocephalic trunk and right common carotid artery: an incidental combination expanding the polymalformative spectrum

• KILT syndrome is a rare congenital cause of deep vein thrombosis in young adults • Inferior vena cava agenesis may coexist with complex arterial malformations • First reported association of KILT syndrome with brachiocephalic trunk agenesis • Comprehensive arterial and venous imaging is essential in unexplained DVT • Recognition of associated anomalies may impact long-term management KILT syndrome (Kidney and Inferior vena cava abnormalities with Leg Thrombosis) is a rare congenital condition combining inferior vena cava (IVC) agenesis, renal anomalies, and deep vein thrombosis (DVT). It typically affects young adults with unprovoked or recurrent DVT. No previous report has described its coexistence with supra-aortic trunk agenesis. A 35-year-old male presented with acute left iliofemoral DVT, six months after an inadequately treated right proximal DVT. He had a known solitary left kidney. CT venography confirmed infrarenal IVC agenesis with extensive collateral drainage, establishing KILT syndrome. CT angiography revealed agenesis of the brachiocephalic trunk and right common carotid artery, with a slender right internal carotid artery reconstituted via the external carotid territory. The right subclavian artery origin was absent, with post-vertebral collateral reconstitution. Despite a 32 mmHg inter-arm systolic pressure gradient, the patient was asymptomatic with adequate intracranial compensation. This case documents an incidental combination of KILT syndrome with brachiocephalic trunk and carotid agenesis. While this arterial anomaly does not warrant routine screening in all KILT patients, recognizing such combinations has implications for cerebrovascular risk assessment and procedural planning. This case also underscores the importance of lifelong anticoagulation from the first DVT episode in IVC agenesis.