Unusual Presentation of Coronary Artery Fistula in Capillary Malformation Arteriovenous Malformation 2 Syndrome: A Case Report

ABSTRACT Capillary malformation‐arteriovenous malformation syndrome (CM‐AVM) is a germline vascular dysplasia that is typically characterized by cutaneous capillary malformations and central nervous system arteriovenous malformations (AVM). We report an atypical presentation of CM‐AVM2 featuring a giant coronary fistula. A 22‐day‐old male exhibited a cardiac murmur, leading to the discovery of a large fistula from the left circumflex coronary artery. The patient developed left eye exophthalmos due to a left‐sided basilar to pontomesencephalic vein fistula. Genetic testing demonstrated a previously reported pathogenic ephrin type B‐receptor 4 ( EPHB4 ) variant c.175G>A, p.Glu59Lys, suggesting a diagnosis of CM‐AVM2 syndrome. A variant of uncertain significance in GATA‐binding factor 2 ( GATA2 ) c.1289C>T, p.Ala430Val was also identified. Due to residual enlargement of the left coronary artery following fistula occlusion, the patient was initiated on warfarin and aspirin for dual anticoagulation and antiplatelet therapy. This uncommon presentation may warrant cardiac imaging for patients with CM‐AVM syndrome presenting with a murmur or other cardiac symptoms. Further investigation is necessary to determine the incidence of cardiac involvement in patients with CM‐AVM syndrome.