Immune thrombocytopenia (ITP) is one of the most common autoimmune diseases. It is an acquired condition which occurs from the auto-antibody mediated destruction of platelets or their impaired production.

There are two forms of ITP:

Acute

• The most common type of ITP.
• Short-term and lasts for approximately 6-months.
• Mainly seen in children and also known as paediatric ITP.
• Commonly has a self-limiting course with children suddenly recovering within 3-months.
• Approximately between 1 and 6.4 annual cases per 100,000 children.
• Can appear at any age, however the principal age is between 2 and 5 years.
• More common among male children.

Chronic 

• Develops over a long period of time and lasts for ≥6-months.
• Annual incidence is roughly between 1 and 6 cases per 100,000 adults.
• Mainly affects adults; however, children and adolescents can get this variation.
• Women have a 2-3-fold higher risk than men; which can be linked to oestrogen.
• Incidence increases with age and peaks around 60, with risk becoming similar between males and females after this age.

Signs and symptoms

It is not uncommon for no symptoms to present, however persistent bleeding is the most evident symptom.

• Petechiae – small, flat red spots under the skin.
• Purpura – red, purple or brownish/yellow spots under the skin.
• Haematoma – clotted blood under the skin which looks or resembles a lump.
• Nosebleeds.
• Bleeding gums.
• Blood in the urine or stool.
• Heavy menstrual bleeding.
• Extreme fatigue.

Causes

The main cause is a malfunctioning immune system, with the immune system attacking and destroying platelets. Also, age-related immune decline and comorbidities can be a factor for the incident of ITP. When the reason for the development of ITP is from a reduced production of platelets, the reason is unknown. Other causal factors include:

• Medicines – antibiotics, antivirals, anti-inflammatory treatments.
• Infections – viral or bacterial.

Risk of thromboembolism

Despite ITP being associated with a low platelet count and bleeding, the risk of both arterial and venous thromboembolism is increased. The explanation for this is that in ITP there is a common mechanism which causes increased platelet activation.

Elevated levels of prothrombotic platelet-derived microparticles and complement activation on antibody-coated platelets support the development of thrombosis in ITP. A review in 2017 found that the presence of antiplatelet antibodies was associated with an elevated risk of thrombosis by >30-fold compared to the general population.

Research from 2024 found that among 26 ITP patients there were 29 VTE and 8 arterial thrombosis with the first event occurring within 5 years after ITP diagnosis. The most common VTE was pulmonary embolism.

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References

• Goncalves, I., Lewis, C., Grainger, B., Dring, R., Lee, N., Pasricha, S.-R., Szer, J., & Mason, K. (2024). Thrombosis in patients with immune thrombocytopenia: incidence, risk, and clinical outcomes. Research and Practice in Thrombosis and Haemostasis, 8(1), 102342–102342. https://doi.org/10.1016/j.rpth.2024.102342.
• Lambert, M. P., & Gernsheimer, T. B. (2017). Clinical updates in adult immune thrombocytopenia. Blood, 129(21), 2829–2835. https://doi.org/10.1182/blood-2017-03-754119.
• Singh, A., Uzun, G., & Bakchoul, T. (2021). Primary Immune Thrombocytopenia: Novel Insights into Pathophysiology and Disease Management. Journal of Clinical Medicine, 10(4), 789-. https://doi.org/10.3390/jcm10040789.
• Sun, S., Urbanus, R. T., Ten Cate, H., de Groot, P. G., de Laat, B., Heemskerk, J. W. M., & Roest, M. (2021). Platelet activation mechanisms and consequences of immune thrombocytopenia. Cells (Basel, Switzerland), 10(12), 3386-. https://doi.org/10.3390/cells10123386.
• Tan, Y., Yan, M., Cheng, Z., & Pan, X. (2021). Pulmonary thromboembolism in immune thrombocytopenia: A report of five cases and a review of the literature. International Journal of General Medicine, 14, 4479–4483. https://doi.org/10.2147/IJGM.S323146.
• Platelet Disorders - Immune Thrombocytopenia (ITP) | NHLBI, NIH.
• Immune Thrombocytopenic Purpura - StatPearls - NCBI Bookshelf (nih.gov).