Right Forearm Arteriovenous Malformation with Dual Osseous Remodeling: Hyperostosis and Erosion of Ulna and Radius.

Arteriovenous malformations (AVMs) are rare vascular anomalies, characterized by direct communications between arteries and veins without an intervening capillary bed, resulting in high-flow shunting. These lesions may be congenital or acquired and can manifest at any age. Although AVMs are more commonly reported in the head, neck, and lower extremities, upper limb involvement is unusual and may pose diagnostic and therapeutic challenges. We report the case of a 63-year-old male presenting with chronic, recurrent swelling, and progressive pain in the right forearm over 4 years, with aggravation in the past 6 months. Clinical examination revealed diffuse swelling over the volar and ulnar aspect of the forearm without overlying skin changes. Imaging with computed tomography angiography and venography demonstrated a large nidus of dilated arterial and venous channels involving the intramuscular and subcutaneous planes, with multiple feeding arteries from the ulnar and interosseous arteries, draining predominantly into the basilic vein. Associated osseous changes in the ulna and radius, including hyperostosis, cortical thickening, periosteal reaction, and focal erosions, were also noted. This case underscores the importance of considering AVM as a differential diagnosis in long-standing extremity swellings, particularly when associated with skeletal changes. Early diagnosis and precise vascular mapping using advanced imaging are essential for effective management and to prevent the complications such as thrombosis, pain, and functional impairment.