Symptoms and causes

Symptoms

Idiopathic thrombocytopenic purpura (ITP) may have no signs and symptoms. When they do occur, they may include:

  • Easy or excessive bruising (purpura)
  • Superficial bleeding into the skin that appears as a rash of pinpoint-sized reddish-purple spots (petechiae), usually on the lower legs
  • Bleeding from the gums or nose
  • Blood in urine or stools
  • Unusually heavy menstrual flow

When to see a doctor

Make an appointment with your doctor if you or your child develops warning signs that worry you.

Bleeding that won't stop is a medical emergency. Seek immediate help if you or your child experiences bleeding that can't be controlled by the usual first-aid techniques, such as applying pressure to the area.

Causes

In some people thrombocytopenia is caused by the immune system mistakenly attacking and destroying platelets. If the cause of this immune reaction is unknown, the condition is called idiopathic thrombocytopenic purpura. Idiopathic means "of unknown cause."

In most children with ITP, the disorder follows a viral illness, such as the mumps or the flu. It may be that the infection triggers the immune system malfunction.

Increased breakdown of platelets

In people with ITP, antibodies produced by the immune system attach themselves to the platelets, marking the platelets for destruction. The spleen, which helps your body fight infection, recognizes the antibodies and removes the platelets from your system. The result of this case of mistaken identity is a lower number of circulating platelets than is normal.

A normal platelet count is generally between 150,000 and 450,000 platelets per microliter of circulating blood. People with ITP often have platelet counts below 20,000. Because platelets help the blood clot, as their number decreases, your risk of bleeding increases. The greatest risk is when your platelet count falls very low — below 10,000 platelets per microliter. At this point, internal bleeding may occur even without any injury.

Risk factors

Idiopathic thrombocytopenic purpura can occur in anyone at almost any age, but these factors increase the risk:

  • Your sex. Women are two to three times more likely to develop ITP than men are.
  • Recent viral infection. Many children with ITP develop the disorder after a viral illness, such as mumps, measles or a respiratory infection.

Complications

A rare complication of idiopathic thrombocytopenic purpura is bleeding into the brain, which can be fatal.

Pregnancy

In pregnant women with ITP, the condition doesn't usually affect the baby. But the baby's platelet count should be tested soon after birth.

If you're pregnant and your platelet count is very low or you have bleeding, you have a greater risk of heavy bleeding during delivery. In such cases, you and your doctor may discuss treatment to maintain a stable platelet count, taking into account the effects on your baby.