Imaging Studies:

• X-ray (1st image): Increased trabeculation and a cystic bone lesion in the proximal femur. 
• MRI (2nd image): T1 weighted image shows flow related signal loss (dark signal) in the area, suggestive of a high-flow malformation (vascular birthmark).
• Conventional Arteriogram (Angiography) (3rd and 4th images): Obvious increased vascularity is seen in the area with an aneurysmal venous abnormality and large draining veins. 

Diagnosis: AVM

Discussion: Arteriovenous malformations are high-flow vascular birthmarks and commonly involve the soft tissues, and in some cases, they may involve the bones. Bone changes related to AVM are not well documented in the literature. This case clearly demonstrates possible bony changes due to high-flow nature of these anomalies. Currently, it is unclear if these bone changes may cause significant weakening.

Treatment: Transcatheter embolization. This patient required multiple embolization procedures (staged).