Bleeding disorders are a group of conditions where blood cannot clot properly. Transfusion of platelets or plasma products may be required to assist with clotting. Red cells may also be required if blood loss is severe.
How does blood clot?
When blood vessels are damaged during injury, platelets and clotting proteins collect at the site of the damage to form a clot, acting like a plug. This allows healing to occur at the site of the injury while preventing blood from escaping the blood vessel. While too much clotting can lead to conditions such as heart attacks and strokes, the inability to form clots can also be a problem due to excessive bleeding. Bleeding can result from abnormal platelets or low platelet counts (eg. Thrombotic Thrombocytopenic Purpura), abnormal or low amounts of clotting proteins (eg. Haemophilia), or abnormal blood vessels.
Thrombotic Thrombocytopenic Purpura
Thrombotic Thrombocytopenic Purpura (TTP) is a condition which results in clotting, low platelet count and bleeding or bruising. Clots form in some blood vessels such as in the kidneys, or in the brain, which can lead to stroke. Another term for clot is ‘thrombosis’, hence the name ‘thrombotic’. Low platelet count 'thrombocytopaenia' results in bleeding which mostly occurs into the skin, forming a type of bruising known as ‘purpura’. The usual treatment for TTP is plasma exchange where an apheresis machine removes the patient’s plasma and replaces it with cryodepleted plasma.
Patients with haemophilia cannot make blood clots properly as they have low levels of a protein essential for blood clotting. This places them at risk of bleeding.
There are two main types of haemophilia:
- Haemophilia A is the most common type and is due to a deficiency of Factor VIII.
- Haemophilia B or Christmas disease is due to a deficiency of Factor IX.
Both types of haemophilia can range from mild to severe depending on how much Factor VIII or IX is missing. Haemophilia is treated by replacing the missing factor protein. Both Factor VIII and IX are available in recombinant and plasma forms.