Von Willebrand Disease
Von Willebrand disease (VWD) is a genetic disorder caused by missing or defective von Willebrand factor (VWF), a clotting protein. VWF binds factor VIII, a key clotting protein, and platelets in blood vessel walls, which help form a platelet plug during the clotting process. The condition is named after Finnish physician Erik von Willebrand, a who first described it in the 1920s.
VWD is the most common bleeding disorder, affecting up to 1% of the US population. It is carried on chromosome 12 and occurs equally in men and women.
People with VWD experience frequent nosebleeds, easy bruising and excessive bleeding during and after invasive procedures, such as tooth extractions and surgery. Women often experience menorrhagia, heavy menstrual periods that last longer than average, and hemorrhaging after childbirth.
There are three main types of VWD based on qualitative or quantitative defects in VWF. A fourth type, acquired VWD, is not hereditary.
- Type 1 VWD is found in 60%-80% of patients. People with type 1 VWD have a quantitative deficiency of VWF. Levels of VWF in the blood range from 20%-50% of normal. The symptoms are usually mild.
- Type 2 VWD is found in 15%-30% of patients. People with type 2 VWD have a qualitative deficiency in their VWF. Type 2 is broken down into four subtypes: type 2A, type 2B, type 2M and type 2N, depending on the presence and behavior of multimers, molecular chains of VWF. Symptoms are mild to moderate.
- Type 3 VWD is found in 5%-10% of patients. People with type 3 VWD have a quantitative deficiency of VWF. Symptoms are typically severe, and include spontaneous bleeding episodes, often into their joints and muscles.
- Acquired VWD. This type of VWD in adults results after a diagnosis of an autoimmune disease, such as lupus, or from heart disease or some types of cancer. It can also occur after taking certain medications.
The best place for patients with bleeding disorders to be diagnosed and treated is at one of the federally-funded hemophilia treatment centers (HTCs) that are spread throughout the country. HTCs provide comprehensive care from skilled hematologists and other professional staff, including nurses, physical therapists, social workers and sometimes dentists, dieticians and other healthcare providers.
A medical health history is important to help determine if other relatives have been diagnosed with a bleeding disorder or have experienced symptoms. Tests that evaluate clotting time and a patient’s ability to form a clot may be ordered. A clotting factor test, called an assay, and tests measuring platelet function also may be performed. The VWF antigen test measures the amount of VWF in blood plasma. Patients with VWD typically have <50% of normal VWF in their plasma. After VWD is confirmed, a test to determine the exact type is performed.
It should be noted that diagnostic testing to confirm VWD may have to be repeated because levels of VWF fluctuate. VWF can rise due to stress, exercise, the use of oral contraceptives, pregnancy and hyperthyroidism.
Treatment for VWD depends on the diagnosis and severity. The mainstay of treatment is DDAVP (desmopressin acetate), the synthetic version of a natural hormone vasopressin,. It stimulates the release of VWF from cells, which also increases FVIII.DDAVP comes in two forms: injectable and nasal spray. Because DDAVP is an antidiuretic, causing the body to retain water, fluid restrictions are important so patients don’t develop hyponatremia, reduced sodium in the bloodstream.
There are a few clotting factor concentrates that are rich in VWF, and are recommended for patients with VWD. These therapies are given by intravenous infusion.
Aminocaproic acid and tranexamic acid are antifibrinolytics agents that prevent the breakdown of blood clots. These drugs are often recommended before dental procedures, to treat nose and mouth bleeds, and for menorrhagia. Antifibrinolytics are taken orally, as a tablet or liquid. MASAC recommends that a dose of clotting factor be taken first to form a clot, then aminocaproic acid, to preserve the clot and keep it from being prematurely broken down.