When you get a small cut, more than likely, it’s no big deal. The bleeding usually stops in seconds, and you go about your day without really thinking about it. When you get a bigger cut, it may take a little bit longer to stop bleeding, but it eventually does after you put a bandage on it. This is because the blood surrounding the cut thickens and clots and quickly stops you from bleeding. This process is called hemostasis. But for people with hemophilia, a mutation that prevents blood from clotting, hemostasis doesn’t work like it should.

It‘s important to stop bleeding to avoid losing too much blood and to help your skin heal. For most people, this is what happens during hemostasis:

1. You cut your finger and blood rushes out.
2. Blood vessels under your skin become narrower to reduce bleeding.
3. Small particles in your blood called platelets immediately stick to the site of injury to form a clot that quickly turns into a plug to stop the bleeding.
4. The platelets send out a signal to get more help to stop the bleeding.
5. Protein in the blood called fibrin helps stabilize the clot to permanently stop the bleeding and let the cut heal.

Most of us—minus the approximately 20,000 people living in the U.S. with hemophilia—have proteins in the blood called coagulation Factor VIII (FVIII) and IX (FIX). People with hemophilia have very low levels of FVIII and FIX in their blood, and they can’t stop bleeding after getting a cut or wound. People with more severe cases of hemophilia can also have frequent, deep, spontaneous bruises; unexplained nosebleeds and brain bleeds; and heavy menstrual periods.

The mutation in the gene that causes hemophilia can be hereditary—meaning that parents pass this gene to their children—or it can be due to a spontaneous change in the gene.

Hemophilia treatment has come a long way over the years. People with this bleeding disorder used to need blood transfusions that contained FVIII and FIX to help them form blood clots. Scientists later found they could remove FVIII and FIX from blood and inject it directly into people with hemophilia even before an injury or surgery to prevent bleeding. FVIII and FIX removed from blood don’t last very long in the body, so shots were needed several times a week to maintain a high enough level to help their blood clot. Recently, however, researchers found a way to make artificial FVIII and FIX in the laboratory that lasts much longer. Now, an injection weekly or once every two weeks helps people with hemophilia better manage their disease.