From the Guidelines
The spleen plays a crucial role in regulating platelet levels in the body, serving as the primary site for platelet storage and removal of old or damaged platelets from circulation. The relationship between platelets and the spleen is complex, with the spleen containing about one-third of the body's platelets at any given time 1. In certain conditions like immune thrombocytopenia (ITP), the spleen may inappropriately destroy healthy platelets, leading to low platelet counts (thrombocytopenia) 1.
Role of the Spleen in Platelet Regulation
The spleen functions as a filter, removing old or damaged platelets from circulation, and when platelets become senescent or damaged, they are recognized and destroyed by specialized macrophages in the spleen 1. This process is essential for maintaining healthy platelet counts and preventing the accumulation of damaged platelets in the body.
Implications for Immune Thrombocytopenia (ITP)
In ITP, the spleen may play a key role in the destruction of healthy platelets, leading to thrombocytopenia 1. Splenectomy (surgical removal of the spleen) is sometimes considered as a treatment option for severe ITP, as it can increase platelet counts by eliminating the main site of platelet destruction. However, splenectomy carries risks, including increased susceptibility to certain infections, so it's typically reserved for cases that don't respond to first-line treatments like corticosteroids or immunoglobulins 1.
Clinical Considerations
After splenectomy, patients require specific vaccinations against encapsulated organisms and may need prophylactic antibiotics 1. The relationship between platelets and the spleen explains why conditions affecting the spleen, such as splenomegaly (enlarged spleen), often result in thrombocytopenia due to increased sequestration of platelets within the enlarged organ 1.
Key Points
- The spleen plays a crucial role in regulating platelet levels in the body
- The spleen serves as the primary site for platelet storage and removal of old or damaged platelets from circulation
- In ITP, the spleen may inappropriately destroy healthy platelets, leading to thrombocytopenia
- Splenectomy is sometimes considered as a treatment option for severe ITP, but carries risks and is typically reserved for cases that don't respond to first-line treatments.
From the Research
Relationship Between Platelets and the Spleen
The spleen plays a crucial role in platelet sequestration, with studies indicating that it can sequester up to 72% of the total platelet mass in hypersplenic conditions 2.
Platelet Sequestration and Splenectomy
- Splenectomy can lead to an increase in platelet count due to the loss of the spleen's ability to sequester platelets 3, 4, 2.
- However, splenectomy has also been associated with an increased risk of thromboembolism, potentially due to the loss of splenic function and changes in platelet quality and function 4, 2.
- Abnormal platelet quality and function have been observed after splenectomy, which may contribute to the increased risk of thromboembolism 2.
Role of the Spleen in Immune Thrombocytopenia
- The spleen is the primary site responsible for platelet destruction in immune thrombocytopenia (ITP) 5.
- Splenectomy can improve thrombocytopenia and reduce anti-platelet antibody production in ITP patients 3, 4, 5.
- However, splenectomy may not completely eliminate anti-platelet immune responses, and antibody-coated platelets and cytotoxic T lymphocytes can persist or change over time 5.
Alternative Therapies to Splenectomy
- Partial splenic embolization (PSE) has been shown to be a safe and effective alternative therapy to splenectomy for patients with steroid-resistant ITP, generating long-term, durable responses 6.
- Thrombopoietin receptor agonists (TPO-RAs) can also be used to increase platelet count and reduce the risk of peri-operative complications in ITP patients undergoing splenectomy 3, 4.