What causes blood clots in children?


Genetic Thrombophilia: Inherited clotting conditions that can increase your child’s tendency to form blood clots.

Acute: A sudden or short-term illness.

Chronic: A long-term illness.

The following can cause blood clots in children:

  • Poor blood flow in the veins can cause blood clots. This may happen when children are confined to bed in the hospital.
  • Damage to the inner lining of veins can cause blood clots. This damage can happen when we place a “central line” catheter, such as a “Port” or “PICC,” in a vein.
    • These are long flexible tubes we may need to insert through your child’s veins.
    • Damage can also happen when certain drugs or toxins circulate in the blood.
  • Inherited clotting conditions can increase your child’s tendency to form blood clots. We call these inherited clotting conditions “genetic thrombophilia.”
  • Other illnesses and certain medications can cause blood clots in children.
  • Birth control pills, patches, or rings that contain estrogen and other hormones increase the risk of blood clots for teenage girls.
  • Occasionally, unusual structure or function of the blood vessels can cause blood clots. Both of these conditions can cause blood clots:
    • In May-Thurner syndrome, a vein in the left leg (iliac vein) narrows.
    • In Paget-Schroetter syndrome, a vein where the arm meets the chest (subclavian vein) narrows.
In most children with blood clots, we find more than one risk factor caused their blood clot.
  • These risk factors often include an acute or chronic illness, such as a severe infection, cancer, an abnormal heart structure, and disorders of the immune system.
  • Sometimes, though not often, we don’t know what causes your child’s blood clot.

Neil A. Goldenberg, MD, PhD

Associate Professor of Pediatrics and Medicine, Johns Hopkins University School of Medicine,
Baltimore, MD, USA

Chief Research Officer and Director, Thrombosis Program,
All Children’s Hospital Johns Hopkins Medicine and All Children’s Research Institute,
St. Petersburg, FL, USA

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