Blood Clotting Disorders in Children

Clotting is the result of a series of chemical changes in blood that are intended to help the body repair damaged blood vessels. Platelets in the blood form a small mass that helps seal a wound and stop the flow of blood.

Illustration of blood components

The body also relies on proteins called clotting factors to create a web of threads to secure the platelet "plug" and hold the blood clot in place.

A blood clot that forms when it's not needed can cause serious problems. The clot may block a vein or artery and interrupt blood flow through the body.

Facts about clotting disorders

Clotting disorders are a group of conditions in which people are more likely than normal to experience excessive clotting. The medical term for this is thrombophilia. These disorders may first be spotted in childhood but are usually identified in adolescence and young adulthood. They are often genetic, meaning they are inherited and present at birth, even if not noticeable. Children who have blood clotting disorders tend to form clots very easily.

Types of clotting disorders

These are common blood clotting disorders:

  • Factor V Leiden. This inherited disorder increases the risk for deep vein thrombosis (clots that appear deep in the body, usually in the thigh or lower leg) and complications with pregnancy, such as miscarriage. It is the most common inherited clotting disorder and occurs most often in children of European descent. Although many people inherit this abnormality, most never have an abnormal blood clot.

  • Prothrombin thrombophilia. This clotting disorder is the second most common type. It also increases the risk for deep vein thrombosis and pregnancy complications, including slowed fetal development and miscarriage. It is also most likely to occur in those of European descent, and only a small percentage of people with this disorder will ever have an abnormal blood clot.

  • Protein C deficiency. The severity of this condition varies from mild, which is most common, to severe. Most people who have it will have no symptoms or simply have an increased risk for deep vein thrombosis during recovery from surgery or periods of immobility. Babies born with the severe form of this condition, however, can develop tiny blood clots throughout their body that prevent blood flow and may cause fatal tissue death.

  • Protein S deficiency. The severity of this condition also varies. As with protein C deficiency, most people who have it will have no symptoms or simply have increased risk for deep vein thrombosis during recovery from surgery or periods of immobility, but those born with the severe form of this condition can develop tiny blood clots that may lead to fatal tissue death.

  • Antithrombin deficiency. This inherited disorder significantly increases the chance of developing abnormal blood clots. About half of those with this disorder will develop at least one clot, usually after adolescence. These clots may cause deep vein thrombosis or pulmonary embolism.

The disorders increase the risk for dangerous blood clots that prevent the flow of blood to organs, such as the brain, lungs, and heart.


Although clotting disorders are usually inherited conditions, some illnesses, such as lupus, may also result in abnormalities that lead to an increased risk for clotting.


A blood clot that blocks needed blood flow requires immediate medical treatment. Symptoms depend on where in the body the clot is located and may include:

  • Sudden swelling in an arm or leg

  • Soreness or pain in an arm or leg

  • Change of skin color to red, pale, or bluish skin, or coolness or warmth over an area of an arm or leg

If a blood clot moves to the lungs, it is a medical emergency. Symptoms include having trouble breathing, chest pain, an unusually fast heartbeat, coughing, a slight fever, and periods of fainting. If you suspect your child has a clot in his or her lungs, call 911 or go to an emergency room immediately.

Diagnosis and treatment

In children, the diagnosis of a clotting disorder is made based on these factors:

  • Description of the symptoms

  • Personal and family medical history

  • Physical examination, which will include an examination of any areas where there is pain, redness, or swelling

  • Blood tests, such as a complete blood count and a platelet count to assess the number of red blood cells, white blood cells, and platelets in the child's blood; clotting tests to determine the level of clotting factors in the child's blood and how long it takes to clot; and genetic tests to check whether the child's blood contains mutations of genes known to cause clotting disorders

Medication is the main treatment for clotting disorders. Anticoagulants, commonly called blood thinners, may be given intravenously in a hospital setting. Sometimes aspirin is used along with these drugs. Your child might need to take daily blood thinner medication for an extended period of time. And, during high-risk periods, your child may need stronger medications to help manage existing clots or prevent clotting.


Serious complications from clotting disorders in children are not common. But problems can occur while they are young or in later years. Clots also can be fatal. These are possible complications:

  • Recurrence of clots—children who survived clots as infants are at greater risk for clots later in life

  • For girls, later problems with pregnancy and delivery

  • Pulmonary embolism, a clot that travels through the blood to the lungs

  • Stroke, if a blood clot blocks blood flow in the brain

  • Death