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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
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The body also relies on proteins called clotting factors. These 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. It may also interrupt blood flow through the body.

Facts about clotting disorders

Clotting disorders are a group of conditions that make people 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. This means that they are inherited and are 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. These are clots that appear deep in the body, usually in the thigh or lower leg. This disorder also increases complications with pregnancy like miscarriage. It is the most common inherited clotting disorder and happens 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. These include slowed fetal development and miscarriage. It is also most likely to occur in those of European descent. 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, like the brain, lungs, and heart.


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


Health care providers use the term venous thromboembolism (VTE) to describe 2 conditions. The 2 conditions are deep vein thrombosis (DVT) and pulmonary embolism (PE). They use the term VTE because the 2 conditions are very closely related. The term is also used because their prevention and treatment are also closely related. A deep vein thrombosis is a blood clot in a large vein deep inside a leg, arm, or other part of the body.

Symptoms may include:

  • Sudden swelling 

  • Soreness or pain 

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

Call your child's health care provider if your child has symptoms that may mean a blood clot.

The clot can separate from the vein and travel to the lungs. In the lungs, the clot can cut off the flow of blood. This is a medical emergency and may cause death.

Symptoms may include;

  • Trouble breathing

  • Chest pain 

  • Fast heartbeat

  • Sweating

  • Coughing, may cough up blood

  • Fever

  • Fainting.

Call 911 if your child has symptoms that may mean a blood clot in the lungs.

Your child may also have bleeding from taking medication to treat clotting problems. If your child has heavy or uncontrolled bleeding call 911. If your child has other signs or symptoms of bleeding, call his or her health care provider. For example, your child may have blood in the urine, bleeding with bowel movements, or bleeding from the nose, gums, or a cut.

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. This will include an examination of any areas where there is pain, redness, or swelling

  • Blood tests. A complete blood count and a platelet count can assess the number of red blood cells, white blood cells, and platelets in the child's blood. Clotting tests can determine the level of clotting factors in the child's blood and how long it takes to clot. And genetic tests can 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