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

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
    • 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
      • Often not diagnosed until adulthood
      • 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
      • Typically diagnosed by 6 years
    • Severe disease (<1% factor activity) – high risk of severe, spontaneous bleeding
      • Usually diagnosed in first year due to spontaneous muscle and joint bleeding
  • Acquired disease is indistinguishable from inherited disease except that it rarely occurs in children

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
Test Name and Number Recommended Use Limitations Follow Up
CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Initial test for suspected bleeding disorder

   
Prothrombin Time 0030215
Method: Electromagnetic Mechanical Clot Detection

Initial test for suspected bleeding disorder

   
Partial Thromboplastin Time 0030235
Method: Electromagnetic Mechanical Clot Detection

Initial test for suspected bleeding disorder

   
Bleeding Disorders (Common) 2003417
Method: Microlatex Particle-Mediated Immunoassay/Platelet Agglutination/Electromagnetic Mechanical Clot Detection

Initial panel test for suspected bleeding disorder

Includes PT, PTT, FVIII activity, FIX activity, FXI activity, VWF activity and antigen

   
Factor VIII, Activity 0030095
Method: Clotting

Diagnose hemophilia A

Monitor factor VIII replacement therapy

Not reliable for hemophilia A carrier determination in at-risk females  
Factor IX, Activity 0030100
Method: Clotting

Diagnose hemophilia B

Monitor factor IX replacement therapy

Not reliable for hemophilia B carrier determination in at-risk females

 
Hemophilia A (F8) 2 Inversions with Reflex to Sequencing and Reflex to Deletion/Duplication 2001614
Method: Inverse Polymerase Chain Reaction/Sequencing/Multiplex Ligation-dependent Probe Amplification

Detect the causal F8 mutation in established cases of hemophilia A

Determine carrier status for females with a family history of hemophilia A

If inversion testing does not explain clinical scenario, F8 gene sequencing will be performed; if gene sequencing does not explain clinical scenario, deletion/duplication testing will be performed

Clinical sensitivity – 51% for inversion testing, 43% for sequencing, and 6% for deletion/duplication analysis

Breakpoints of large F8 deletions/duplications will not be determined

F8 deep intronic or promoter mutations, with the exception of the common intron 1 and 22A inversions, will not be detected

Rare diagnostic errors may occur due to primer- or probe-site mutations

 
Hemophilia B (F9) Sequencing 2001578
Method: Polymerase Chain Reaction/Sequencing

Detect causal F9 mutation in established cases of hemophilia B

Determine carrier status for women with a family history of hemophilia B

Contradicted for diagnostic or carrier testing of individuals with a previously identified familial F9 mutation

Clinical sensitivity – 97%

Deep intronic mutations and gene duplications will not be detected in patients of either sex

Large deletions will not be detected in females

Rare diagnostic errors may occur due to primer site mutations

 
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Hemophilia A (F8) Sequencing 2001747
Method: Polymerase Chain Reaction/Sequencing

Determine F8 mutation in individuals with mild or moderate disease

Carrier testing for those with a family history of mild or moderate disease

Hemophilia A (F8) Deletion/Duplication 2001751
Method: Polymerase Chain Reaction/Multiplex Ligation-dependent Probe Amplification
Carrier or diagnostic testing for individuals with relatives with a known large F8 deletion or duplication
Hemophilia A (F8) 2 Inversions 2001759
Method: Inverse Polymerase Chain Reaction/Electrophoresis

Carrier or diagnostic testing for individuals with relatives with a known inversion of intron 1 or 22A

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

Fetal testing for the F8 intron 1 or 22A inversion when the mother is a known inversion carrier