Hemophilia - Factor VIII or IX Deficiency

Diagnosis

Indications for Testing

• Spontaneous or prolonged bleeding suggestive of coagulation disorder
• Family history of hemophilia 
• Acute or recent onset bleeding accompanied by prolonged partial thromboplastin time (PTT)

Initial Laboratory Testing for Coagulation Disorders

• CBC with platelet count – normal in hemophilia A, B
• Prothrombin time (PT)/PTT
  • PT – normal in hemophilia A, B
  • PTT – prolonged in moderate and severe hemophilia
    • May not be prolonged in mild cases or in female carriers
    • Prolonged PTT that corrects in a mixing study suggests factor deficiency
    • PTT that does not correct with mixing study suggests an inhibitor
      • Incubated mixing studies are often necessary to identify FVIII inhibitors
• Thrombin clotting time and plasma concentration of fibrinogen – normal in hemophilia A and B

Laboratory Testing for Hemophilia 

• FVIII activity level – decreased in hemophilia A
• FIX activity level – decreased in hemophilia B
  • Not reliable for carrier status detection in females
  • Measurement in neonate may need to be repeated when family history of mild disease exists
• von Willebrand factor (VWF) level – normal
  • Because VWF is a carrier for FVIII, von Willebrand disease (VWD) should be ruled out in patients with decreased FVIII levels
  • A rare subtype of VWD (type 2N) has isolated low FVIII activity with normal VWF level and mimics hemophilia A
    • Specialized coagulation or genetic testing can be used to distinguish these disorders
• Genetic testing
  • Patient risk should be calculated by a clinical geneticist using laboratory results and family history 
  • Confirm the causative F8 or F9 mutation in affected individuals
  • Determine carrier status in at-risk females

Prognosis

• Improved prognosis with the advent of FVIII and FIX replacement
• Major disability from bleeding – joint disease 
• Leading cause of death from bleeding – intracranial hemorrhage

Differential Diagnosis

• VWD
• Rare coagulation factor deficiencies
  • FII, FV, FVII, FX, FXI, FXII
  • Fibrinogen
  • Deficiencies of factor XII, prekallikrein, and high molecular weight kininogen prolong the PTT but do not result in a bleeding tendency
• Fibrinolytic disorders
• Qualitative platelet function disorders

Clinical Background

Hemophilia A and hemophilia B are bleeding disorders caused by genetic mutations in the F8 or F9 genes that result in deficiencies of factor VIII (FVIII) or factor IX (FIX) respectively. These disorders are clinically indistinguishable and present with bleeding symptoms ranging from mild to severe, depending on the underlying defect.

Epidemiology

• Incidence
  • Hemophilia A – 1/4,000-5,000 male births worldwide; rare in females
  • Hemophilia B – 1/25,000 male births worldwide; rare in females
  • Acquired hemophilia – 1-2/1,000,000 worldwide
    • <1/1,000,000 in children
• Age
  • Severe disease – usually detected in first year of life
  • Moderate disease – detected before age 5
  • Mild disease – detected later in life
  • Acquired disease – bimodal peaks at 20-40 years and 60-90 years
• Types
  • Hemophilia A – FVIII deficiency
  • Hemophilia B – FIX deficiency
  • Acquired hemophilia – autoimmune disorder caused by antibodies to FVIII or, rarely, FIX

Inheritance

• Hemophilia A
  • X-linked recessive F8 mutations
    • Penetrance – 100% in males, 10% in females
    • Female offspring of affected males are obligate carriers
      • 10% of female carriers are symptomatic, typically with mild disease
    • ~ 1,800 F8 sequence variants reported to date
  • Some genotype/phenotype correlations exist for hemophilia A
    • Molecular causes for severe disease
      • Intron 22A inversion – 48%
      • Point mutations – 43%
      • Large gene deletions – 6%
      • Intron 1 inversion – 3%
    • Molecular causes for moderate to mild disease
      • Point mutations or small insertions/deletions – 98%
      • Large gene deletions – <1%
  • In probands who appear to have no family history of hemophilia, >80% of mothers are identified as carriers; the remaining 10-15% of probands show de novo F8 mutations
• Hemophilia B
  • X-linked recessive F9 mutations
    • Penetrance – 100% in males, 10% in females
    • Female offspring of affected males are obligate carriers
      • 10% of female carriers are symptomatic, typically with mild disease
    • ~33-50% of apparently isolated hemophilia B cases result from de novo mutations
    • ~900 F9 sequence variants reported to date

Clinical Presentation

• Presentation of hemophilia A is clinically indistinguishable from hemophilia B
• Excessive bleeding – occurs spontaneously or from trivial injury
  • Common bleeding manifestations – hemarthrosis, hematomas, gastrointestinal bleeding, genitourinary bleeding
• Frequency and severity of excessive bleeding based on FVIII or FIX activity
  • Mild disease (6-35% factor activity) – bleeding may occur with major trauma or surgery; no spontaneous bleeding
    • Carrier females – 10% have mild disease (<40% factor activity) and are at risk for excessive bleeding
  • Moderate disease (1-5% factor activity) – bleeding may occur with minimal trauma or minor surgery; spontaneous bleeding rare
  • Severe disease (<1% factor activity) – high risk of severe, spontaneous bleeding
• Acquired disease is indistinguishable from inherited disease except that it rarely occurs in children
  • Associated conditions
    • Autoimmune – systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, Sjögren syndrome, Goodpasture syndrome, myasthenia gravis, inflammatory bowel disease
    • Cancer – lymphomas, plasma cell dyscrasia, myelodysplastic syndrome
    • Dermatologic – psoriasis, pemphigus 
    • Hepatitis B or C infection (acute)
    • Drugs

Treatment

• Refer to a federally funded hemophilia treatment center (HTC) for assessment, education, and genetic consultation
• Severely affected individuals – to prevent spontaneous bleeding, prophylactic FVIII or FIX infusions (factor concentrates, recombinant FVIII or IX) to maintain activity at 1-3%
• Mild hemophilia A – desmopressin for prophylaxis or treatment
• Factor replacement (factor concentrates, recombinant) used for acute bleeding
• Carrier females – monitor for delayed postpartum bleeding unless baseline FVIII or FIX clotting activity is previously identified as normal
• At-risk individuals – until disease is ruled out or diagnosed and appropriately treated, avoid antiplatelet drugs, intramuscular injections, activities with high trauma risk, circumcision
• Administer antifibrinolytic agents in applicable situations

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Hemophilia A (F8) Sequencing 2001747 Method: Polymerase Chain Reaction/Sequencing	Detect F8 mutations in patients with mild-moderate hemophilia A
Hemophilia A (F8) Deletion/Duplication 2001751 Method: Polymerase Chain Reaction/Multiplex Ligation-dependent Probe Amplification	Detect F8 mutations in patients with severe hemophilia
Hemophilia A (F8) 2 Inversions 2001759 Method: Inverse Polymerase Chain Reaction/Electrophoresis	Detect F8 mutations in patients with severe hemophilia
Factor VIII Activity with Reflex to Bethesda Quantitative, Factor VIII 0030026 Method: Clotting
Factor IX Activity with Reflex to Bethesda Quantitative, Factor IX 0030032 Method: Clotting	If FIX is >20%, no further testing will be performed; if FIX activity is ≤20%, Bethesda quantitative (FIX) will be added
Factor XI, Activity 0030110 Method: Clotting
von Willebrand Panel 0030125 Method: Clotting/Platelet Agglutination/Microlatex Particle-Mediated Immunoassay	Distinguish FVIII deficiency from VWD
Thrombin Time with Reflex to Thrombin Time 1:1 Mix 0030260 Method: Clotting	Distinguish factor deficiencies from factor inhibitors, such as antibodies against FXIII
Fibrinogen 0030130 Method: Electromagnetic Mechanical Clot Detection	Initial workup for suspected bleeding disorder
Hemophilia A (F8) 2 Inversions, Fetal 2001755 Method: Inverse Polymerase Chain Reaction/Electrophoresis	Prenatal diagnosis of F8 intron 22A and intron 1 inversions