How is the severity of hemophilia A classified?

Updated: Apr 08, 2020
  • Author: Douglass A Drelich, MD; Chief Editor: Srikanth Nagalla, MBBS, MS, FACP  more...
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The classification of the severity of hemophilia has been based on either clinical bleeding symptoms or on plasma procoagulant levels; the latter are the most widely used criteria. Classification according to plasma procoagulant levels is as follows:

  • Severe hemophilia - FVIII level less than 1% of normal (< 0.01 IU/mL)

  • Moderate hemophilia - FVIII level 1-5% of normal (0.01-0.05 IU/mL)

  • Mild hemophilia - FVIII level more than 5% but less than 40% of normal (>0.05 to < 0.40 IU/mL)

Severe disease presents in children younger than 1 year and accounts for 43-70% of hemophilia A cases. Moderate disease presents in children aged 1-2 years and accounts for 15-26% of cases. Mild disease presents in children older than 2 years and accounts for 15-31% of cases.

Clinical bleeding symptom criteria have been used because patients with FVIII levels of less than 1% occasionally have little or no spontaneous bleeding and appear to have clinically moderate or mild hemophilia. Furthermore, the reverse is true for patients with procoagulant activities of 1-5%, who may present with clinically severe disease.

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