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USMLE Step 1Haematology and oncologyEP 09 of 14

Von Willebrand disease vs haemophilia: the labs that separate them

Both conditions can give a long PTT, so the PTT alone cannot separate them. The bleeding pattern, the bleeding time and the factor levels can.

  • 5:32 video
  • 3 min read
  • 15 sources
  • Published 15 Nov 2026
Video lesson · 5:32 · Watch on YouTubeSeries: Hematology: Anemia, Coagulation & Oncology Basics · @medservatory
Chapters (10)
By the end of this lesson

Distinguish von Willebrand disease from haemophilia A and B by bleeding pattern, bleeding time, PTT and factor levels, using the two roles of von Willebrand factor: platelet adhesion and factor VIII carrier.

The short version

  1. Von Willebrand factor has two jobs: it anchors platelets to exposed collagen, and it carries factor VIII and protects it from breakdown.
  2. Haemophilia is deep bleeding (joints and muscles) with a normal bleeding time and, usually, a prolonged PTT.
  3. Von Willebrand disease is mucocutaneous bleeding with a usually prolonged bleeding time and a PTT that may be normal.
  4. Factor levels settle it: low factor VIII or IX in haemophilia (below 40 IU/dL; below 1 in severe disease); low von Willebrand factor, with factor VIII normal or reduced, in von Willebrand disease.
  5. Haemophilia is treated by replacing the missing factor; type 1 von Willebrand disease can be treated with desmopressin.

Von Willebrand disease vs haemophilia: two bleeds, one long PTT

A boy wakes with a hot, swollen knee after a trivial bump. A girl, in another family, has nosebleeds that run on and on, and very heavy periods. Both can show a long PTT. So how do we tell them apart?

This lesson compares von Willebrand disease vs haemophilia using four things: the bleeding pattern, the bleeding time, the PTT and the factor levels.

Two stages of haemostasis, and where von Willebrand factor sits

In primary haemostasis, platelets stick to the damaged vessel wall and to each other, forming a soft plug. In secondary haemostasis, the coagulation cascade makes fibrin, which firms that plug into a clot.[7][1]

Von Willebrand factor (VWF) works in the first stage: it is the glue that anchors platelets to exposed collagen.[1][6]

It has a second job. It carries factor VIII in the blood and protects it from breakdown.[1][6]

Haemophilia A and B: a pure fibrin-stage problem

Factor VIII is missing in haemophilia A, and factor IX in haemophilia B. Both genes sit on the X chromosome, so inheritance is X-linked recessive and patients are almost always male.[2][3]

Platelets still stick, so the soft plug forms and the bleeding time is normal. But the fibrin behind it is weak.[8][9]

That causes deep bleeds: into joints, called haemarthroses, and into muscles.[2][3]

Haemophilia severity by factor activity
SeverityFactor activity (IU/dL)
SevereBelow 1
Moderate1–5
MildAbove 5, below 40

Severity follows factor activity.[2][11]

Von Willebrand disease: mucocutaneous bleeding and three types

Von Willebrand disease is mainly a platelet-stage problem. The bleeding is mucocutaneous: nosebleeds, gum bleeding, easy bruising and heavy periods.[1][6]

Von Willebrand disease types
TypeWhat is wrongInheritance
Type 1Partial lack of the factor (about 60–80% of cases)Autosomal dominant
Type 2A faulty factorMostly autosomal dominant
Type 3Complete absence; the most severeAutosomal recessive

The type 1 share is quoted differently by different sources, which is why the range is wide.[1][4][5]

The labs: bleeding time, PTT and factor levels, with a worked example

The platelet count is usually normal in both conditions, and so is the PT.[1][9]

The bleeding time separates them: usually prolonged in von Willebrand disease, because platelets cannot adhere properly, and normal in haemophilia.[1][8][9]

The PTT depends on the intrinsic factors, including factor VIII and factor IX. In haemophilia it is usually prolonged. In von Willebrand disease it may be prolonged, because factor VIII falls when its carrier is low, or it may be normal.[2][1]

The factor levels settle it.[1][2]

Haemophilia vs von Willebrand disease
FeatureHaemophilia A or BVon Willebrand disease
Bleeding patternDeep: joints, musclesMucocutaneous
Platelet countUsually normalUsually normal
PTNormalNormal
Bleeding timeNormalUsually prolonged
PTTUsually prolongedMay be prolonged, or normal
Factor levelsLow factor VIII or IXLow VWF; factor VIII normal or reduced

An eight-year-old boy bleeds into his right knee. Platelets and PT are normal, the PTT is prolonged, the bleeding time is normal, and factor VIII activity is 2% of normal, which is 2 IU/dL (100% = 100 IU/dL).[2][3]

Grading the severity
  1. Factor VIII activity 2% = 2 IU/dL
  2. Severe is below 1; moderate is 1–5; mild is above 5 and below 40
  3. 2 lies between 1 and 5
  4. Moderate haemophilia A

Knee bleed, normal bleeding time and a prolonged PTT fit haemophilia, and the factor level grades it.[2][3][8]

Platelet look-alikes: Glanzmann thrombasthenia and Bernard-Soulier syndrome

Two inherited platelet disorders can also cause mucosal bleeding with a long bleeding time, so they are worth separating from von Willebrand disease.[10][15]

Two platelet look-alikes
DisorderDefectPlatelet countaPTT
Glanzmann thrombastheniaGlycoprotein IIb/IIIa (αIIbβ3): defective aggregationNormalNormal
Bernard-Soulier syndromeGlycoprotein Ib (the platelet receptor for VWF): defective adhesion to VWFLow, with giant plateletsNormal

In both, the coagulation cascade is intact, so the aPTT does not rise. In von Willebrand disease it can, because factor VIII falls with its carrier.[10][15][1]

Treatment: replace the factor, or release stored VWF

Haemophilia is treated by replacing the missing factor, or with newer drugs such as emicizumab that stand in for factor VIII.[3][11][12]

Type 1 von Willebrand disease can be treated with desmopressin, which releases stored von Willebrand factor from endothelial cells.[1][4][12]

Practice question

Original · USMLE style
Your turnQB-MS-S1-HEME-005-01

A 17-year-old girl has had frequent nosebleeds since childhood and heavy menstrual bleeding. She bruises easily and has never had bleeding into a joint. Her mother has similar symptoms. Laboratory studies show:

Results
Platelet count240 × 10⁹/L (reference 150–400 × 10⁹/L)
Prothrombin time12 s (reference 11–13.5 s)
Activated partial thromboplastin time41 s (reference 25–35 s)
Bleeding timeProlonged
Which of the following is the most likely underlying abnormality?
Pick one option. Your answers stay on this device.

Common questions

What is the difference between von Willebrand disease and haemophilia?

Haemophilia is a fibrin-stage problem with deep bleeds into joints and muscles and a normal bleeding time. Von Willebrand disease is mainly a platelet-stage problem with mucocutaneous bleeding and a usually prolonged bleeding time.

Why can von Willebrand disease cause a prolonged PTT?

Von Willebrand factor carries factor VIII and protects it from breakdown, so factor VIII falls when its carrier is low. The PTT may therefore be prolonged, or it may be normal.

Is bleeding time normal in haemophilia?

Yes. Platelets still stick, so the soft plug forms and the bleeding time is normal. It is usually prolonged in von Willebrand disease.

How is haemophilia severity graded?

By factor activity: below 1 IU/dL is severe, 1–5 is moderate, and above 5 but below 40 is mild.

Transcript

Read the full narration, by chapter686 words

0:00Two patients, two bleeds, both with a long PTT

Two patients, two very different bleeds. A boy wakes with a hot, swollen knee after a trivial bump. A girl, in another family, has nosebleeds that run on and on, and very heavy periods. Both can show a long PTT. So how do we tell them apart? Today: tell von Willebrand disease from haemophilia by bleeding pattern, bleeding time, PTT and factor levels. In primary haemostasis,

0:27Primary and secondary haemostasis: the two stages

platelets stick to the damaged vessel wall and to each other, forming a soft plug. In secondary haemostasis, the coagulation cascade makes fibrin, which firms that plug into a clot.

0:42Von Willebrand factor: platelet glue and factor VIII carrier

Von Willebrand factor works in the first stage: it is the glue that anchors platelets to exposed collagen. But it has a second job: it carries factor eight in the blood and protects it from breakdown. So it sits in both stages, and losing it can hurt both.

0:59Haemophilia A and B: X-linked, deep bleeds, severity by factor activity

Haemophilia is a pure fibrin-stage problem: factor eight is missing in haemophilia A, factor nine in haemophilia B. Both genes sit on the X chromosome, so inheritance is X-linked recessive and patients are almost always male. Platelets still stick, so the soft plug forms and the bleeding time is normal. But the fibrin behind it is weak. That causes deep bleeds: into joints, called haemarthroses, and into muscles. Severity follows factor activity: below one international unit per decilitre is severe, one to five moderate, and above five, up to 40, mild.

1:42Von Willebrand disease: mucocutaneous bleeding, types 1, 2 and 3

Von Willebrand disease is mainly a platelet-stage problem. The bleeding is mucocutaneous: nosebleeds, gum bleeding, easy bruising, heavy periods. About 60 to 80% of cases are type one, a partial lack of the factor, autosomal dominant. Type two is a faulty factor. Type three is complete absence, autosomal recessive and the most severe.

2:10The labs: platelets, PT, bleeding time, PTT, factor levels

Now the labs. The platelet count is usually normal in both, and so is the PT. The bleeding time separates them: usually prolonged in von Willebrand disease, because platelets cannot adhere properly, and normal in haemophilia. The PTT depends on factor eight. In haemophilia it is usually prolonged. In von Willebrand disease it may be prolonged, because factor eight falls when its carrier is low, or it may be normal. The factor levels settle it. Haemophilia: very low factor eight or nine. Von Willebrand disease: low von Willebrand factor, with factor eight normal or reduced.

2:53Worked example and treatment

An example. An 8-year-old boy bleeds into his right knee. Platelets and PT are normal, PTT is prolonged, bleeding time is normal, factor eight activity is 2%, which is two international units per decilitre. Moderate haemophilia A, since two lies between one and five. Haemophilia is treated by replacing the missing factor, or with newer drugs such as emicizumab that stand in for factor eight. Type one von Willebrand disease can be treated with desmopressin, which releases stored von Willebrand factor from endothelial cells.

3:32Practice question

Your turn. A 17-year-old girl has had frequent nosebleeds since childhood and heavy menstrual bleeding. She bruises easily and has never bled into a joint. Her mother has similar symptoms. Platelet count is 240, PT is 12 seconds, APTT is 41 seconds, and bleeding time is prolonged. Which of the following is the most likely underlying abnormality? A, factor nine deficiency. B, factor eight deficiency from an X-linked mutation. C, von Willebrand factor deficiency or dysfunction. D, glycoprotein IIb/IIIa deficiency. E, glycoprotein Ib deficiency. Pause here and decide.

4:25Answer and explanation

A and B are out: haemophilia is X-linked, mostly male, with joint bleeds and a normal bleeding time. D is out: Glanzmann thrombasthenia causes mucosal bleeding too, but the APTT is normal. E is out: Bernard-Soulier syndrome gives a low platelet count with giant platelets, and hers is normal. So the answer is C. Mucosal bleeding, long bleeding time, mildly long APTT from low factor eight, dominant family history: von Willebrand disease.

5:00Recap and next lesson

Three things to keep. One: haemophilia is deep bleeding, a normal bleeding time and, usually, a long PTT. Two: von Willebrand disease is mucosal bleeding and a usually long bleeding time, with a PTT that may be normal. Three: von Willebrand factor is platelet glue and factor eight carrier. Next, the anticoagulants: heparin, warfarin and the direct oral drugs.

Sources

Numbers in the text, e.g. [1], point here
  1. Federici AB, et al. Diagnosis and Treatment of Von Willebrand Disease and Rare Bleeding Disorders. J Clin Med 2017. europepmc.org/article/PMC/PMC5406777
  2. Factor VIII and Factor IX Activity Measurements for Hemophilia Diagnosis. Semin Thromb Hemost 2023. europepmc.org/article/PMC/PMC10421651
  3. Haemophilia and joint disease. J Comorb 2011. europepmc.org/article/PMC/PMC5556421
  4. Von Willebrand disease. Res Pract Thromb Haemost 2018. europepmc.org/article/PMC/PMC5974913
  5. Von Willebrand disease. Res Pract Thromb Haemost 2023. europepmc.org/article/PMC/PMC10439443
  6. Von Willebrand factor review. J Blood Med 2023. europepmc.org/article/PMC/PMC9987238
  7. Interplay between platelets and coagulation. Blood Rev 2021. europepmc.org/article/PMC/PMC7354275
  8. Clinical and laboratory approaches to hemophilia A. Iran J Med Sci 2015. europepmc.org/article/PMC/PMC4430880
  9. Haemophilia cohort. J Family Med Prim Care 2021. europepmc.org/article/PMC/PMC8132779
  10. Inherited Platelet Disorders: An Updated Overview. Int J Mol Sci 2021. europepmc.org/article/PMC/PMC8123627
  11. Alvarez-Payares JC, et al. Clinical Scenarios in Hospitalized Patients With Hemophilia. Cureus 2026; Olivieri M, Königs C. When and How to Start Prophylaxis in Children with Hemophilia. Transfus Med Hemother 2026. europepmc.org/article/PMC/PMC13134844 · europepmc.org/article/PMC/PMC13183381
  12. Srivastava A, Mahlangu J, Pipe SW. Guidelines for management of hemophilia: why, what, and how? (editorial). Res Pract Thromb Haemost 2025. europepmc.org/article/PMC/PMC12158498
  13. Ramamurthy NR, et al. Platelet Function Disorders: Glanzmann Thrombasthenia and Type 2 Von Willebrand Disease (case report). Cureus 2026. europepmc.org/article/PMC/PMC13390610
  14. Leebeek FWG. New Developments in Diagnosis and Management of Acquired Hemophilia and Acquired von Willebrand Syndrome. Hemasphere 2021. europepmc.org/article/PMC/PMC8171371
  15. Chemlal I, et al. Glanzmann Thrombasthenia in a 14-Month-Old Infant (case report). Cureus 2026; Salem ML, et al. Bernard-Soulier Syndrome: Identification of a Novel GP1BB Variant in a Mauritanian Patient (case report). Mol Genet Genomic Med 2026. europepmc.org/article/PMC/PMC13264495 · europepmc.org/article/PMC/PMC12823461

Bleeding time is taught here as an exam concept; it has largely been replaced in clinical practice. Reference ranges are the common textbook ones: PT 11 to 13.5 s, aPTT 25 to 35 s, platelets 150 to 400 x 10^9/L.

The practice question is original and its patient is synthetic. Every fact is checked against the sources above in independent accuracy reviews. Always follow your local guidelines and your own laboratory’s ranges.

Image credits. Illustrations: Servier Medical Art (smart.servier.com), CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), adapted (recoloured, outlined, labelled): "Coagulation" (three drawings), "Knee, parasagittal section", "Blood test", "Syringe". Platelet and von Willebrand factor (recoloured) art: NIAID NIH BioArt Source (bioart.niaid.nih.gov), public domain. Nose icon: Health Icons (healthicons.org), CC0. Original diagrams: the cascade sketch, pedigree, severity ruler, lab report, type cards, calendar, bruise and gum sketches, collagen and shield drawings. No AI-generated teaching images.

Corrections. None so far. Spotted an error? Email info@medservatory.com with the lesson code MS-S1-HEME-005.

For exam study only, not medical advice. Read the medical disclaimer.

In this series

Playlist on YouTube
← Previous · EP 08Coagulation cascade: PT vs aPTT, pathway by pathway
  1. EP 01Microcytic anaemia: four causes, four iron fingerprints5:37
  2. EP 02Hepcidin: why iron falls in inflammation5:34
  3. EP 03B12 vs folate deficiency: MMA, homocysteine and the nerves5:23
  4. EP 04Intravascular vs extravascular haemolysis: site and labs5:27
  5. EP 05G6PD deficiency vs hereditary spherocytosis, by mechanism5:36
  6. EP 06Sickle cell disease pathophysiology: HbS to vaso-occlusion5:26
  7. EP 07Primary haemostasis: platelet adhesion, activation and aggregation5:53
  8. EP 08Coagulation cascade: PT vs aPTT, pathway by pathway5:21
  9. EP 09Von Willebrand disease vs haemophilia: the labs that separate them5:32
  10. EP 10Anticoagulants: target, monitoring test and reversal agent5:34
  11. EP 11Heparin-induced thrombocytopenia: why a low count clots5:29
  12. EP 12DIC vs TTP vs HUS: mechanism and the PT/PTT5:33
  13. EP 13AML vs ALL vs CML vs CLL: leukemia classification made simple5:44
  14. EP 14Oncogenes vs tumour suppressor genes: one hit or two5:17