Post-transfusion purpura

Post-transfusion purpura (PTP) is a rare but serious complication that can occur after a blood transfusion. It is characterized by a sudden onset of thrombocytopenia (low platelet count) and the development of purpura, which are purple spots on the skin caused by bleeding underneath.

Pathophysiology

PTP is primarily caused by the production of alloantibodies against platelet antigens. The most common antigen involved is the HPA-1a (Human Platelet Antigen-1a). When a patient who lacks this antigen receives a transfusion containing HPA-1a positive platelets, their immune system may produce antibodies against these platelets, leading to their destruction.

Clinical Presentation

Patients with PTP typically present with severe thrombocytopenia, often less than 10,000 platelets per microliter, approximately 5 to 10 days after a transfusion. This is accompanied by the appearance of purpura, which are small, red or purple spots on the skin. Other symptoms may include epistaxis (nosebleeds), hematuria (blood in urine), and gastrointestinal bleeding.

Purpura on the skin, a common symptom of post-transfusion purpura

Diagnosis

The diagnosis of PTP is based on the clinical presentation and the history of recent blood transfusion. Laboratory tests reveal severe thrombocytopenia. Serological tests can identify the presence of anti-platelet antibodies, particularly anti-HPA-1a antibodies.

Treatment

The mainstay of treatment for PTP is the administration of high-dose intravenous immunoglobulin (IVIG), which can help to rapidly increase platelet counts. In some cases, plasmapheresis may be used to remove the offending antibodies from the circulation. It is also crucial to avoid further transfusions of HPA-1a positive blood products.

Prognosis

With appropriate treatment, the prognosis for patients with PTP is generally good, with platelet counts typically returning to normal within several days to weeks. However, without treatment, the condition can be life-threatening due to the risk of severe bleeding.

Prevention

Preventive measures include screening for platelet antibodies in patients with a history of PTP and providing antigen-negative blood products for future transfusions.

Related pages

• Thrombocytopenia
• Blood transfusion
• Immune thrombocytopenic purpura