About Hemophilia

Hemophilia is a rare bleeding disorder in which the blood does not clot normally. Hemophilia is a monogenic disease (a disease that is caused by a genetic defect in a single gene). There are two types of hemophilia caused by mutations in genes encoding protein factors that help the blood clot and stop bleeding when blood vessels are injured. Individuals with hemophilia experience bleeding episodes after injuries and spontaneous bleeding episodes that often lead to joint disease such as arthritis. The most frequent forms of hemophilia affect males.


Underlying Genetic Cause of Disease

The most prevalent form of the disease, hemophilia A, is caused by a defect in the Factor 8 gene, while defects in the Factor 9 gene lead to hemophilia B.

Hemophilia Symptoms

  • Hemophilia can be mild, moderate or severe
  • Severe hemophilia patients may experience bleeding following an injury and or may have spontaneous bleeding episodes into their joints and muscles (severity depends on the underlying disease)
  • Excessive bleeding with obvious cause such as an injury
  • Prolonged bleeding from cuts, surgery, injury or tooth extraction
  • Spontaneous bleeding episodes that can range in severity: joint bleeding, nosebleeds, easy bruising, gastrointestinal tract and urinary tract bleeding
  • Women with mild hemophilia may experience menorrhagia, heavy menstrual periods, and may hemorrhage after childbirth

Hemophilia affects 1 in 5,000 male births

An estimated 400,000 people worldwide are living with hemophilia

All disease stats are according to the Centers for Disease Control and Prevention (CDC)



Estimated number of babies born with hemophilia A each year


Estimated number of people with hemophilia in the United States


Estimated number of people with hemophilia A


Estimated number of people with hemophilia B

Sangamo’s Therapeutic Approach

Sangamo is developing an adeno-associated virus (AAV) based gene therapy for hemophilia A and a genome editing treatment for hemophilia B that uses our proprietary zinc finger nuclease (ZFN) genome editing technology. To learn more about how our genomic therapies work, click the More Information button, below.


Patient Stories