# Haemophilia and von Willebrand Disease > Haemophilia and von Willebrand disease for NEET-PG Pathology: factor VIII deficiency, vWF function, ristocetin assay and desmopressin. - Canonical URL: https://prepelephant.com/topics/neet-pg/pathology/haemophilia-von-willebrand-pathology - Exam / course: NEET-PG · Subject: Pathology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Haemophilia and von Willebrand Disease", PrepElephant, https://prepelephant.com/topics/neet-pg/pathology/haemophilia-von-willebrand-pathology ## Direct answer Haemarthrosis in a boy whose maternal uncle had the same problem is the classic presentation of haemophilia A, an X-linked recessive deficiency of factor VIII that produces deep, delayed bleeding into joints and muscles with a prolonged aPTT and a normal PT, bleeding time and platelet count. von Willebrand disease, the commonest inherited bleeding disorder, is qualitatively different: defective von Willebrand factor impairs both platelet adhesion and factor VIII survival, so mucocutaneous bleeding — menorrhagia, epistaxis, dental bleeding — dominates and the bleeding time is prolonged. Desmopressin raises factor VIII and vWF in mild haemophilia A and most type 1 vWD, making it the shared first-line answer for both. ## What you must remember - Haemophilia A (factor VIII, about 80-85 per cent of cases) and haemophilia B (factor IX, Christmas disease) are both X-linked recessive; a third of haemophilia A cases arise from new mutations. - Severity tracks factor levels: below 1 per cent severe (spontaneous haemarthroses), 1-5 per cent moderate, above 5 per cent mild (bleeds only after trauma or surgery). - Deep bleeding pattern: haemarthroses (knee, elbow, ankle) causing arthropathy, muscle haematomas, retroperitoneal and intracranial bleeds; petechiae are absent because platelets are normal. - Laboratory: prolonged aPTT correcting on mixing study, normal PT, normal platelet count, normal bleeding time; specific factor assays settle A versus B. - vWF has two jobs — carrying factor VIII in plasma and mediating platelet adhesion to collagen via GPIb — which is why vWD mixes a factor-deficiency phenotype with a platelet-type phenotype. - vWD types: type 1 partial quantitative deficiency (commonest, autosomal dominant), type 2 qualitative variants (2A, 2B — which binds platelets too well and thrombocytopenia worsens with desmopressin, 2M, 2N mimicking haemophilia A), type 3 severe autosomal recessive absence. - Ristocetin induces vWF-GPIb binding, so impaired ristocetin-induced platelet aggregation indicates vWD; vWF antigen and factor VIII levels are low in type 1. - Desmopressin (DDAVP) releases stored factor VIII and vWF from endothelial Weibel-Palade bodies — first line for mild haemophilia A and type 1 vWD; factor concentrates are used for severe disease and haemophilia B. - Acquired haemophilia: autoantibodies to factor VIII in the elderly, pregnancy or autoimmune disease — aPTT fails to correct on mixing and inhibitor titres (Bethesda assay) guide bypassing agents. - Inhibitors develop in roughly a quarter of severe haemophilia A patients on frequent concentrate exposure, the main modern therapeutic challenge. ## A typical exam case and its resolution A four-year-old has a swollen, painful right knee after minor playground trauma; the same knee swelled six months ago, and his maternal uncle bled for days after circumcision. Counts, PT and bleeding time are normal; aPTT is 68 seconds (control 30), correcting on the mixing study, and factor VIII assay returns 1 per cent. This is severe haemophilia A. Management proceeds in layers: factor VIII replacement acutely (around 30-50 per cent for a joint bleed, near 100 per cent for intracranial or surgical bleeding) with rest, ice and elevation; inhibitor screening with a Bethesda assay after repeated exposure; and prophylaxis with regular factor VIII infusions or emicizumab, a bispecific antibody bridging factors IXa and X that substitutes factor VIII function in severe disease. Avoid intramuscular injections and aspirin, and enrol the family in comprehensive haemophilia care — India's national network supplies factor concentrates. Contrast the girl whose mother and sister have heavy periods and who bruises after dental cleaning: prolonged bleeding time, reduced vWF antigen, impaired ristocetin aggregation — type 1 vWD, treated with desmopressin and tranexamic acid, a different bleeding phenotype from the boy's haemarthrosis. ## Where students slip The exam repeatedly distinguishes the two bleeding phenotypes, and candidates blur them. Haemophilia gives deep, delayed, pressure-unresponsive bleeds with a normal bleeding time; vWD gives mucosal, immediate-onset bleeding with a prolonged bleeding time — the child with "haemophilia" who has epistaxis and petechiae is usually vWD or a platelet disorder. Second, sex-linked pattern questions: a bleeding girl with an affected father and carrier mother suggests the rare type 3 vWD or a homozygous state, not "female haemophilia," though true symptomatic carriers of haemophilia exist (skewed X-inactivation, Turner syndrome). Third, the type 2B trap — desmopressin can worsen thrombocytopenia in type 2B vWD because the abnormal vWF binds platelets excessively, a detail that separates a top-rank answer. Finally, a failure of the mixing study to correct means acquired haemophilia with autoantibody, treated with bypassing agents and immunosuppression rather than simple factor replacement. ## Frequently asked questions ### Which coagulation test is abnormal in haemophilia and why? The aPTT is prolonged because factors VIII and IX sit in the intrinsic pathway; PT, platelet count and bleeding time remain normal. ### What two physiological functions does von Willebrand factor serve? It acts as the carrier protein stabilising factor VIII in plasma, and as the bridge mediating platelet adhesion to subendothelial collagen through GPIb. ### Which drug is first line in mild haemophilia A and type 1 vWD? Desmopressin (DDAVP), which releases endothelial stores of factor VIII and vWF; it is avoided in type 2B vWD. ### What distinguishes type 3 from type 1 von Willebrand disease? Type 3 is an autosomal recessive virtual absence of vWF with severe bleeding from birth, whereas type 1 is a common autosomal dominant partial deficiency. ### How is acquired haemophilia distinguished from congenital haemophilia A in the laboratory? The aPTT fails to correct on mixing study and a factor VIII inhibitor is quantified by the Bethesda assay, typically in an elderly patient without a family history. ### Which agent now substitutes for factor VIII function in severe haemophilia A with inhibitors? Emicizumab, bridging factors IXa and X, with recombinant factor VIIa for acute bleeds.