6.3 Hemophilia, von Willebrand Disease, and Coagulopathies

A toddler who limps after a minor bump, an adolescent with a swollen knee the morning after basketball, and a school-age child who hit a coffee table with his head are the CPHON coagulopathy cases. Hemophilia A, hemophilia B, and von Willebrand disease (vWD) are not interchangeable product problems. The nurse names the missing protein, the bleed pattern, and whether the next syringe is factor, a mimetic, desmopressin, or a von Willebrand-containing concentrate.

Hemophilia A versus B, inheritance, and bleed geography

Hemophilia A is factor VIII deficiency. Hemophilia B is factor IX deficiency. Both are X-linked: males are typically affected; females may be symptomatic carriers if lyonization is skewed. Severity tracks residual factor activity in broad bands: severe disease (typically less than 1%) bleeds spontaneously into joints; moderate disease bleeds with modest trauma; mild disease may present only after surgery or dental work. Do not wait for a family history. About one-third of cases are new mutations.

Hemarthrosis is the signature musculoskeletal bleed. Blood in the joint causes pain, warmth, and loss of motion; repeated bleeds create a target joint and chronic hemophilic arthropathy. Early factor, rest, ice, and staged return to motion beat “walk it off.” Iliopsoas bleeds present as groin or flank pain, hip flexion, and sometimes femoral-nerve symptoms; they can hide a large volume of blood. A 12-year-old with hemophilia A who refuses to straighten the hip after a stumble is not “just a pulled muscle” until factor has gone in and imaging, if needed, is arranged.

Intracranial hemorrhage after head trauma is the life-threatening bleed. In severe hemophilia, even a seemingly minor head bump can seed a subdural or intracerebral hematoma. Mucosal bleeding—epistaxis, gum oozing, heavy menses in carriers or in vWD—is more typical of platelet–von Willebrand physiology than of classic hemophilia, though hemophilia can still bleed from the mouth after dental work.

Replacement: standard, extended half-life, and emicizumab

On-demand or prophylactic factor VIII (hemophilia A) or factor IX (hemophilia B) remains the specific replacement. Extended-half-life products lengthen intervals for prophylaxis; they are still factor, still disease-specific, and still dosed by the hemophilia clinic’s protocol—not by a floor nurse inventing units per kilogram from memory on the exam. Teach venous access, home infusion competence, and that a swollen joint is a treat-now event, not a wait-for-clinic-hours event.

Emicizumab is a bispecific monoclonal antibody that mimics factor VIII function by bridging activated factor IX and factor X. It is subcutaneous prophylaxis for hemophilia A, including many children with inhibitors. It is not a hemophilia B drug. Breakthrough bleeds still need factor VIII (or a bypassing agent per protocol). Combining emicizumab with activated prothrombin complex concentrates (aPCCs) has been associated with thrombosis and thrombotic microangiopathy; teach caution. Many protocols avoid aPCC or restrict it tightly and prefer recombinant factor VIIa for selected breakthrough bleeds on emicizumab. Do not invent a milligram-per-kilogram aPCC cap as an ONCC number; know the interaction is dangerous and that you call the hemophilia center before stacking bypassing agents.

A 4-year-old with severe hemophilia A on weekly emicizumab who wakes with a hot, swollen knee still needs a breakthrough hemostatic plan. Emicizumab prophylaxis is not a reason to withhold factor.

Desmopressin, vWD types, and the ristocetin idea

Desmopressin releases stored factor VIII and von Willebrand factor from endothelium. It can treat mild hemophilia A and type 1 vWD for minor procedures. It does not treat hemophilia B (no factor IX is stored that way) and is not adequate as sole therapy in type 3 vWD, where stores are essentially absent. Tachyphylaxis appears with closely repeated doses. The nursing trap is hyponatremia: restrict free water, avoid hypotonic floods, and watch toddlers who will drink continuously if handed a sippy cup after the dose. A 7-year-old given desmopressin before dental extraction who then drinks liters of water is a seizure risk, not a “well-hydrated” success.

Von Willebrand disease is the most common inherited bleeding disorder. Type 1 is a partial quantitative deficiency. Type 2 is qualitative (2A, 2B, 2M, 2N—recognize that quality, not only quantity, can fail). Type 3 is near-absent VWF and behaves like severe hemophilia plus mucosal bleeding. Labs at the level this exam expects: VWF antigen (how much protein), VWF activity (classically ristocetin cofactor or related GPIb-binding assays—how well it works), and factor VIII (which VWF protects). You do not need to interpret every subtype panel at the bench; you do need to know that “vWD” is not one product order.

Head injury, sports, and what not to inject

Head injury in hemophilia: treat first, image in parallel. Infuse the appropriate factor immediately for significant head trauma or neurologic change. Do not hold factor in the CT queue so that “product is not wasted if the scan is normal.” A normal early scan does not always close observation; a delay to factor can finish the bleed the scanner has not yet shown. A 9-year-old with hemophilia B who struck his head on a table gets factor IX on the way to imaging, not after the radiology report.

Sports counseling is individualized. Swimming, running, and similar lower-impact activities are generally encouraged on prophylaxis. High-impact collision and unsanctioned tackling are discouraged in severe disease. The goal is participation with a bleed plan, not lifelong bubble wrap. School nurses need the product name, the fever-versus-bleed number, and instructions that intramuscular injections and NSAIDs are generally avoided because of hematoma risk and platelet dysfunction. Vaccines are given subcutaneously when possible or with factor cover per the hemophilia clinic. Acetaminophen is the usual first analgesic for mild pain; ketorolac intramuscularly is the wrong reflex.

The CPHON product is a family that can name A versus B, infuse or access prophylaxis, treat a head bump before the scanner, keep water modest after desmopressin, and call before anyone combines emicizumab with an aPCC.