ITP vs. TTP: Key Differences in 2 Platelet Disorders

Easy bruising, frequent nosebleeds, tiny spots under the skin, and low platelet counts are symptoms and signs that may point to immune thrombocytopenia (ITP), thrombotic thrombocytopenic purpura (TTP), or another condition. Doctors use additional symptoms and tests to tell these conditions apart.

Platelets are tiny blood cell fragments that help stop bleeding after a cut or injury. Both ITP and TTP cause low platelet counts, but they do so in different ways.

Understanding how these conditions are similar and how they differ can help you ask the right questions at your next medical appointment.

What Are the Common Symptoms of ITP and TTP?

ITP most often causes bruising and bleeding in the skin or mucous membranes. TTP is a medical emergency because platelet-rich clots form in small blood vessels and can damage the brain, kidneys, heart, and other organs.

ITP Symptoms

Some people with ITP have no symptoms at all. Bleeding becomes more likely as the platelet count falls, but symptoms can occur at different platelet levels in different people.

Symptoms may include bruises that appear seemingly out of nowhere, petechiae (tiny red or purple dots), bleeding gums, or nosebleeds that seem to start for no clear reason. Other symptoms of ITP include:

• Blood in the urine or stool
• Heavier menstrual bleeding than usual
• Fatigue (extreme tiredness that doesn’t improve with rest)
• Headaches

“I was always exhausted,” a myITPteam member said. “I had headaches, easy bruising, nosebleeds, petechiae, and developed hematomas after injections. My periods were three times heavier.”

ITP may develop suddenly or gradually. It often causes bleeding in the skin or mucous membranes, but serious internal bleeding can occur in rare cases.

TTP Symptoms

Since TTP causes tiny blood clots to form in small blood vessels throughout the body, specific symptoms depend on which organs are affected.

In the brain, TTP can cause:

• Headaches
• Confusion
• Trouble speaking
• Vision changes
• Seizures, stroke, or coma

On the skin, it can cause:

• Paleness
• Jaundice (yellowing of the skin or whites of the eyes)
• Bruising and petechiae, similar to ITP

In the kidneys, it can cause:

• Low urine output
• Blood in the urine

Kidney involvement varies in TTP. Some people have mild changes, whereas others develop significant acute kidney injury.

Other symptoms of TTP include:

• Low-grade fever
• Nausea or vomiting
• Extreme weakness
• Gastrointestinal symptoms, such as diarrhea, abdominal pain, nausea, or vomiting
• Shortness of breath

Some people with TTP notice only vague symptoms at first, such as fatigue or a mild headache, which can make the condition difficult to recognize early.

How Do Doctors Tell ITP and TTP Apart?

When you have easy bruising, your doctor will first ask questions about your symptoms, medical history, and any medications you take. This information helps narrow down the possible causes before testing begins.

No single test can confirm an ITP diagnosis. Instead, doctors diagnose ITP by ruling out other causes of a low platelet count. Your doctor may order blood tests such as:

• Complete blood count and peripheral blood smear — A complete blood count measures your platelet count and other blood cells, and a peripheral blood smear lets doctors examine blood cells under a microscope. Schistocytes (fragmented red blood cells) support a thrombotic microangiopathy such as TTP.
• Blood tests for infections — Tests for HIV and hepatitis C are commonly included when evaluating possible ITP. Hepatitis B testing may also be recommended before certain treatments or in some situations.
• Blood tests for other possible causes — Depending on your symptoms and medical history, your doctor may order tests for autoimmune diseases, thyroid disease, pregnancy, or other conditions that can cause a low platelet count.
• Blood tests for signs of organ injury — TTP can affect the brain, kidneys, heart, and other organs. Blood tests that show organ injury may raise concern for TTP but don’t confirm the diagnosis on their own.
• ADAMTS13 activity test — An ADAMTS13 activity level below 10 percent strongly supports TTP when considered along with symptoms and other test results. Because TTP can become life-threatening quickly, treatment may begin before the test results are available.

In some cases, your doctor may also recommend a bone marrow test if another blood or bone marrow disorder is suspected.

TTP is diagnosed using the full clinical picture, including a low platelet count, evidence of red blood cell destruction, organ involvement, and severely reduced ADAMTS13 activity. Although organ symptoms are common, they’re not required for the diagnosis.

TTP usually causes sudden, serious symptoms that often lead people to seek emergency medical care. In contrast, many people with ITP have few or no symptoms when they’re diagnosed.

Why Do ITP and TTP Require Different Treatment Approaches?

Although ITP and TTP both cause low platelet counts, they’re treated in different ways because the underlying causes are different. Treatment also depends on the type of TTP. Immune TTP and congenital TTP require different approaches.

Plasma Exchange

Urgent plasma exchange is a standard treatment for immune TTP, but it’s not used to treat ITP. Plasma exchange removes antibodies that block ADAMTS13 while replacing the missing enzyme through donor plasma. Congenital TTP is treated by replacing ADAMTS13, which may include recombinant ADAMTS13 when available.

Platelet Transfusions

In TTP, doctors generally avoid platelet transfusions because they may worsen clot formation. However, they may be used for life-threatening bleeding or before an urgent procedure after careful specialist evaluation.

In ITP, platelet transfusions may be used for severe or life-threatening bleeding. They may also be given before an urgent invasive procedure when the platelet count needs to rise quickly. Platelet transfusions are usually combined with other ITP treatments because the immune system may rapidly destroy the transfused platelets.

Medications

Treatment for immune TTP usually includes plasma exchange and corticosteroids. Caplacizumab may be added to block the interaction between VWF and platelets, helping prevent tiny clots from forming. Rituximab may be used during an acute episode or for relapsing or hard-to-treat disease by reducing the production of antibodies against ADAMTS13.

Because caplacizumab doesn’t correct the underlying ADAMTS13 problem, it’s used together with plasma exchange and immunosuppressive treatment.

Treatment for ITP is different. Not everyone with ITP needs immediate treatment. Careful monitoring may be appropriate if bleeding is absent or mild and the platelet count is at a safe level.

When treatment is needed, corticosteroids are often used first. Intravenous immunoglobulin (IVIG) may be added when a faster increase in platelet count is needed. IVIG, which is made from donated antibodies and given through a vein, can temporarily reduce immune-mediated platelet destruction and raise the platelet count.

If ITP doesn’t respond well enough to these treatments, several other medications are available.

Join the Conversation

On myITPteam, people come together to gain a new understanding of ITP and share their stories with others who understand life with ITP.

Have you or someone you care about been diagnosed with ITP or TTP? What helped you make sense of it, and what do you wish someone had told you sooner? Share your experience in the comments below.