The Propagation of Hemophilic Arthropathy - the Role of Abnormal Angiogenesis and Vascular Remodeling in Recurrent Joint Bleeding in Adults with Hemophilia

Neoangiogenesis and vascular remodeling in the hypertrophic synovium of arthropathic hemophilic joints may disturb vascular integrity and contribute to repeated bleeding (A von Drygalski, et al. Vascular Remodeling Underlies Re-Bleeding in Hemophilic Arthropathy; ASH 2015; Abstract ID 78677). However, it is difficult to distinguish the importance of the contribution of abnormal vascular structures to hemophilic joint bleeding from the contribution of low clotting factor levels. This is because most prophylactic clotting factor replacement strategies are designed to avoid trough levels below 1-5%, but not to fully correct the factor deficiency.

This report reveals the importance of aberrant angiogenesis for joint bleeding in two hemophilia patients whose clotting factor activity levels were constantly normal or near normal. The first patient had severe Hemophilia A with normalized Factor (f)VIII activity levels after liver transplantation 6 years previously. Abnormal vascularization of elbows, knees and ankles (absent bleeding) was detected by musculoskeletal ultrasound and Power Doppler (PD). Three months after the baseline exam the patient experienced severe elbow bleeding associated with new vascular changes on PD. These changes were characterized by pronounced confluent, patchy vascular signals and numerous enlarged and thickened vessels by angiography consistent with acute and chronic vascular remodeling. Bleeding could not be controlled by increasing fVIII activity to supra-normal levels, and ultimately required synovial embolization. The second patient has severe Hemophilia B and presented shortly after left knee joint replacement with fluctuating knee bleeding for many months associated with pronounced dynamic vascular changes on PD. Neither bleeding nor vascular changes were prevented by daily fIX treatment which maintained near normal plasma fIX activity levels. Within one year, additional chronic bleeding with vascular changes developed in the left elbow and left ankle and remained unresponsive to intense factor replacement.

These cases provide several insights. First, vascular changes in hemophilic arthropathy persist and evolve in dynamic fashion even in the presence of normal clotting factor activities. Second, vascular disturbance and leakiness contributed to bleeding independent of clotting factor activity levels as exemplified by the first patient and as suggested by the second patient. Third, the sequence of bleeding events in the second patient suggests that at least some of the observed vascular abnormalities are mediated systemically. These observations provide clinical evidence in support of the hypothesis that neoangiogenesis and vascular remodeling contribute to hemophilic joint bleeding and should lead to new studies of the pathophysiology of vascular remodeling in such joints. Targeting angiogenesis may emerge as a new treatment strategy to enhance the effectiveness of clotting factor replacement hemophilic arthropathy.