The platelet puzzle: What’s really happening in your body with ITP
Last updated July 21, 2025, by Lindsey Shapiro, PhD
Fact-checked by PatrÃcia Silva, PhD
Immune thrombocytopenia is an autoimmune blood disorder that happens when the immune system mistakenly attacks the body’s platelets. Healthy platelets are needed for proper blood clotting.
Understanding how platelets work in a healthy body — and how ITP destroys them — will make it easier for you to know what to expect when living with this rare disease.
What are platelets?
To understand ITP, it’s key to know exactly what platelets do. Think of platelets, also known as thrombocytes, as a natural bandage to stop bleeding after an injury.
These small, disk-shaped cell fragments are made in the bone marrow and circulate in the blood. When a blood vessel is injured, platelets travel to it and cluster together to form a type of plug, or seal, that prevents blood loss from the injury site. This process, called hemostasis, involves three basic steps:
- adhesion, where circulating platelets travel to the damaged blood vessel and stick to it
- activation, when the adhered platelets change their form, release substances, and recruit more platelets to facilitate hemostasis
- aggregation, where the platelets stick together to plug up the damaged blood vessel.
These actions trigger a chain of events called the coagulation cascade that helps stabilize and secure the clot to lead to the best possible bleed control.
Maintaining the right balance of platelets in the blood is very important. A normal count ranges from about 150,000 to 450,000 per microliter of blood.
Having too many platelets, a condition called thrombocytosis, can increase the risk of harmful blood clots that prevent blood flow through the body. Having too few platelets is called thrombocytopenia and it can increase the risk of excessive bleeding — such as what happens from ITP.
How the immune system misfires in ITP
The immune system normally identifies and destroys harmful invaders such as bacteria and viruses, while recognizing the body’s own tissues and leaving them alone. But in autoimmune conditions, this defense system misfires and mistakenly attacks healthy parts of the body.
ITP is an autoimmune disorder involving erroneous immune attacks that target platelets. Immune cells generate self-reactive antibodies, or autoantibodies, that bind to platelets and mark them for destruction by other immune cells in the spleen called macrophages.
The bone marrow tries to compensate by making more platelets, but it generally can’t keep up, causing blood platelet levels to drop. Sometimes, the disease-driving autoantibodies also attach to platelet precursors in the bone marrow to inhibit new platelet production, further contributing to thrombocytopenia.
Generally, it is not known why ITP causes the immune system to attack platelets. For most people, there isn’t a connection to any other disease (primary ITP). Though sometimes, ITP develops due to another condition that is believed to prime the immune system to be more reactive, such as an infection or autoimmune disorder (secondary ITP).
How ITP affects the body
The autoimmune attacks in ITP mean that there aren’t enough healthy platelets to seal broken blood vessels and start blood clotting. The poor platelet function leaves a person susceptible to bleeding that’s hard to stop.
However, the risk of substantial bleeding usually only becomes an issue when the platelet count is below 50,000 platelets per microliter. This is why the goal of many ITP treatments is to keep it from reaching this low level.
If your platelet counts get low enough, you may notice:
- easily bruising or bleeding, even from very minor injuries
- red, purple, or brown dots (petechiae) or patches (purpura) from under-the-skin bleeding
- bleeding from the gums or nose
- excessive or prolonged menstrual bleeding.
Less often, ITP causes serious internal bleeding, including in the digestive system or brain.
You might also start to feel extreme tiredness or fatigue. This could be related to anemia, where bleeding has led to a lack of healthy red blood cells to carry oxygen through the body. It could also be associated with underlying ITP triggers.
ITP symptoms can take two forms:
- acute ITP, where symptoms appear suddenly but go away on their own within six months
- chronic ITP, where symptoms last for more than six months, but can come and go.
The daily impact of living with ITP
ITP — especially when it’s chronic — can lead to a wide range of physical and emotional challenges that interfere with daily life and affect your well-being.
Fatigue and the risk of bleeding may make it harder to do your usual activities.
You may find you need more help with everyday tasks than you used to, especially if you have a low platelet count and the activity could cause an injury. You or your child with ITP may also have to avoid certain recreational activities that could cause bleeding, such as contact sports.
Still, platelet counts and treatment responses can have a major impact on how much ITP affects your life:
- If your platelets are high enough that there’s no significant bleeding risk, you may be able to live your life with few symptoms and without active treatment, but you’ll still need to be monitored to make sure it doesn’t change.
- If your platelet counts are persistently low, you may experience frequent ITP symptoms. Work with your doctor to find the treatment that is most successful at lessening ITP’s impact on your daily life. Treatments can work by either increasing platelet production or preventing the ITP immune system from destroying existing ones.
Even when ITP is well controlled, you may still feel stressed or anxious about future disease relapses and bleeding events. It’s important to stay on top of your mental health and get support when you need it.
By carefully following an ITP monitoring schedule and a treatment plan that minimizes bleeding and prioritizes self-care and mental health, many people with ITP can live full and active lives.
Bleeding Disorders News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
