Many people with von Willebrand disease don't know it because the signs are mild or absent. The most common sign of the condition is abnormal bleeding. The severity of the bleeding varies from one person to another.

If you have von Willebrand disease, you might experience:

• Excessive bleeding from an injury or after surgery or dental work

• Nosebleeds that don't stop within 10 minutes

• Heavy or long menstrual bleeding

• Blood in your urine or stool

• Easy bruising or lumpy bruises

Signs and symptoms of von Willebrand disease in women

Signs and symptoms of a heavy period that may indicate von Willebrand disease include:

• The presence in your menstrual flow of blood clots greater than 1 inch (2.5 centimeters) in diameter

• The need to change your menstrual pad or tampon more often than hourly

• The need to use double sanitary protection to control menstrual flow

• Symptoms of anemia, including tiredness, fatigue or shortness of breath

The usual cause of von Willebrand disease is an inherited abnormal gene that controls von Willebrand factor, a protein that plays a key role in blood-clotting. When you have low levels of this protein or it doesn't work as it should, small blood cells called platelets cannot stick together properly, nor can they attach themselves normally to the blood vessel walls when an injury has occurred. The result is interference with the clotting process, and, sometimes, uncontrolled bleeding.

Von Willebrand factor carries an additional substance, called factor VIII, that helps stimulate clotting. Many people with von Willebrand disease also have low levels of factor VIII. This is also one of the substances involved in another inherited clotting disorder called hemophilia. But unlike hemophilia, which mainly affects males, von Willebrand disease affects males and females and is usually milder.

Rarely, von Willebrand disease can develop later in life in people who didn't inherit an abnormal gene from a parent. This is known as acquired von Willebrand disease, and it's likely caused by another medical condition.

Von Willebrand disease has several types:

• Type 1. In this most common form of von Willebrand disease, levels of von Willebrand factor are low. In some people, levels of factor VIII also are low. Signs and symptoms are usually mild.

• Type 2. In this type, which has several subtypes, the von Willebrand factor you do have doesn't function properly. Signs and symptoms tend to be more significant.

• Type 3. In this rare type, von Willebrand factor is absent and levels of factor VIII are low. Signs and symptoms may be severe, such as bleeding into the joints and muscles.

• Acquired von Willebrand disease. This type isn't inherited from your parents. It develops later in life.

The main risk factor for von Willebrand disease is having a family history of it. A parent can pass the abnormal gene for the disease to his or her child.

Most cases are "autosomal dominant inherited" disorders, which means you only need an abnormal gene from one parent to be affected. If you have the gene for von Willebrand disease, you have a 50 percent chance of transmitting this gene to your offspring.

The most severe form of the condition (type 3) is "autosomal recessive," which means both of your parents have to pass an abnormal gene to you.

Complications of von Willebrand disease may include:

• Anemia. Women who experience heavy menstrual bleeding can develop iron deficiency anemia.

• Swelling and pain. If abnormal bleeding occurs in the joints or soft tissue, swelling and severe pain can result.

• Death from bleeding. Rarely, someone with von Willebrand disease may experience uncontrolled bleeding that can be life-threatening and needs emergency medical attention.