Preclinical studies in mice and dogs with hemophilia have resulted in long-term correction of the bleeding disorders and, in some cases, a permanent cure. Preliminary results in human trials of gene therapy for hemophilia B have yielded encouraging results, but hemophilia A has proved more problematic, given the much larger size of FVIII DNA and the frequent development of neutralizing antibodies. [59] Implantation of liver-derived stem cells that have been expanded in vitro is under consideration, as these could theoretically induce a steady-state production of quantities of factor sufficient to prevent spontaneous bleeding. [60]
In December 2017, Rangarajan et al reported sustained rises in FVIII levels and declines in bleeding rates in patients with severe hemophilia A who received gene therapy with a single intravenous dose of valoctocogene roxaparvovec, a codon-optimized adeno-associated virus serotype 5 (AAV5) vector encoding a B-domain–deleted human FVIII. In the seven participants who received a high dose of of valoctocogene roxaparvovec, FVIII activity levels remained in the normal range 1.5 years after gene transfer, and their annualized bleeding rate dropped from 16.5 to 0. All participants were able to completely discontinue prophylactic FVIII infusions, and none developed FVIII inhibitors. [61, 62]
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Coagulation pathway.
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The hemostatic pathway. APC = activated protein C (APC); AT-III = antithrombin III; FDP = fibrin degradation products; HC-II = heparin cofactor II; HMWK = high-molecular-weight kininogen; PAI = plasminogen activator inhibitor; sc-uPA = single-chain urokinase plasminogen activator; tc-uPA = two-chain urokinase plasminogen activator; TFPI = tissue factor pathway inhibitor; tPA = tissue plasminogen activator
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Structural domains of human factor VIII. Adapted from: Stoilova-McPhie S, Villoutreix BO, Mertens K, Kemball-Cook G, Holzenburg A. 3-Dimensional structure of membrane-bound coagulation factor VIII: modeling of the factor VIII heterodimer within a 3-dimensional density map derived by electron crystallography. Blood. Feb 15 2002;99(4):1215-23; Roberts HR, Hoffman M. Hemophilia A and B. In: Beutler E, Lichtman MA, Coller BS, et al, eds. Williams Hematology. 6th ed. NY: McGraw-Hill; 2001:1639-57; and Roberts HR. Thoughts on the mechanism of action of FVIIa. Presented at: Second Symposium on New Aspects of Haemophilia Treatment; 1991; Copenhagen, Denmark.
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Possible genetic outcomes in individuals carrying the hemophilic gene.
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Photograph of a teenage boy with bleeding into his right thigh as well as both knees and ankles.
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Photograph of the right knee in an older man with a chronically fused, extended knee following open drainage of knee bleeding that occurred many years previously.
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Photograph depicting severe bilateral hemophilic arthropathy and muscle wasting. The 3 punctures made into the left knee joint were performed in an attempt to aspirate recent aggravated bleeding.
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Radiograph depicting advanced hemophilic arthropathy of the knee joint. These images show chronic severe arthritis, fusion, loss of cartilage, and joint space deformities.
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Radiograph depicting advanced hemophilic arthropathy of the elbow. This image shows chronic severe arthritis, fusion, loss of cartilage, and joint space deformities.
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Photograph of a hemophilic knee at surgery, with synovial proliferation caused by repeated bleeding; synovectomy was required.
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Large amount of vascular synovium removed at surgery.
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Microscopic appearance of synovial proliferation and high vascularity. If stained with iron, diffuse deposits would be demonstrated; iron-laden macrophages are present.
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Large pseudocyst involving the left proximal femur.
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Transected pseudocyst (following disarticulation of the left lower extremity due to vascular compromise, nerve damage, loss of bone, and nonfunctional limb). This photo shows black-brown old blood, residual muscle, and bone.
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Dissection of a pseudocyst.
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Transected pseudocyst with chocolate brown-black old blood.
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Photograph of a patient who presented with a slowly expanding abdominal and flank mass, as well as increasing pain, inability to eat, weight loss, and weakness of his lower extremity.
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Plain radiograph of the pelvis showing a large lytic area.
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Intravenous pyelogram showing extreme displacement of the left kidney and ureter by a pseudocyst.
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Photograph depicting extensive spontaneous abdominal wall hematoma and thigh hemorrhage in an older, previously unaffected man with an acquired factor VIII inhibitor.
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Magnetic resonance image of an extensive spontaneous abdominal wall hematoma and thigh hemorrhage in an older, previously unaffected man with an acquired factor VIII inhibitor.
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Coagulation Cascade
