Transfusion medicine
Transfusion side effects
Post-transfusion purpura (PTP)

Editor-in-Chief: Debra Zynger, M.D.
Kyle Annen, D.O.

Topic Completed: 18 October 2019

Revised: 8 November 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: Post-transfusion purpura [title]

Kyle Annen, D.O.
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Cite this page: Annen K. Post-transfusion purpura (PTP). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/transfusionmedposttransfusionpurpura.html. Accessed December 16th, 2019.
Definition / general
  • Post-transfusion purpura is a rare but serious complication of a blood component transfusion in which severe thrombocytopenia occurs 5 - 10 days after the transfusion event
  • Bleeding may be severe
  • Risk of significant morbidity from bleeding complications with a > 10% mortality rate
  • Self limiting but due to the severity of complications treatment is warranted
  • IVIG is the mainstay of treatment
Essential features
  • Immune condition of severe thrombocytopenia occurring 5 - 10 days after a transfusion
  • Classically occurs after an RBC transfusion but any blood component can trigger the immune process (RBCs, platelets, plasma)
  • Transfusion recipient has antibodies against human platelet specific antigens (HPA) acquired through prior transfusion, transplant or pregnancy
  • F:M = 26:1, but incidence in men increases in age > 65 (Am J Hematol 1996;52:205, Transfusion 2015;55:284)
Terminology
  • PTP (post-transfusion purpura)
  • RBC (red blood cell)
  • HPA (human platelet antigen)
  • HLA (human lymphocyte antigen)
  • ELISA (enzyme linked immunosorbent assay)
  • IVIG (intravenous immune globulin)
Pathophysiology
  • Antiplatelet alloantibodies to human platelet antigens (HPA), usually due to prior transfusion, transplant or pregnancy
  • Anti-HPA-1a is the most common culprit
  • Other HPA antibodies have been implicated
  • Anti-HPA antibody destroys autologous platelets; mechanism is not fully understood
Clinical features
  • Symptoms:
    • Severe, sudden thrombocytopenia (< 10K/uL)
    • Bleeding (mucosal or gastrointestinal)
    • Petechiae or purpura
Laboratory
  • Human platelet antigen (HPA) testing is a highly specialized methodology and is performed at reference labs:
    • Detection of HPA antibodies by immunofluorescence
    • Enzyme linked immunoassay (ELISA)
    • Platelet genotyping (PCR)
    • Monoclonal antibody specific immobilization of platelets assay (MAIPA) (Ann Hematol 2014;93:309)
Case reports
Treatment
  • Self limiting: untreated will persist for 7 - 28 days
  • Platelet transfusion is generally not helpful in the acute phase, even HPA matched platelets are destroyed (Am J Hematol 1979;6:71)
  • IVIG, high dose 400 - 500 mg/Kg per day for 5 days
    • 1 g/Kg for two days in severe cases
  • Glucocorticoids
  • Therapeutic plasma exchange (Acta Med Scand 1978;203:539)
  • Prevention:
    • Patient with known history of post-transfusion purpura should receive washed RBCs
    • Platelet transfusions should be crossmatched or HPA matched products
Sample assessment & plan
  • Assessment: Jane Doe is a 63 year old woman who presented 11 days after PRBC transfusion with severe thrombocytopenia, altered mental status and diffuse petechiae. Send out testing identified the patient has both HLA class I antibodies and is homozygous for HPA-1b platelet antigen, with an antibody to HPA-1a. Further review of history reveals the patient has had 3 pregnancies, with one child affected by neonatal alloimmune thrombocytopenia at birth.
  • Plan: The patient presentation and laboratory workup are consistent with a diagnosis of post-transfusion purpura (PTP).
    • Recommend starting IVIG at 1g/kg/day for three days.
    • Platelets negative for the HPA-1a antigen have been requested. In the acute phase of the disease, platelet transfusion is not usually beneficial, however as this patient has an intracranial hemorrhage from the low platelets, we will issue platelet products as needed. Platelets usually have poor survival after transfusion due to existing patient antibodies.
    • If the patient needs an RBC transfusion, we will issue washed products. Please allow extra time to prepare this product (2 hours).
Differential diagnosis
  • Thrombotic thrombocytopenic purpura
    • Severe thrombocytopenia and microangiopathic hemolytic anemia
    • Schistocytes on peripheral smear
    • Fever, renal dysfunction and neurological dysfunction may be present
  • Drug induced thrombocytopenia
    • History of medication or beverage (quinine water) proximate to thrombocytopenia
    • Only occurs in presence of drug; complete recovery with removal of drug
  • Heparin induced thrombocytopenia (HIT)
    • Venous or arterial thrombosis
    • Platelet count rarely drops < 20k/uL
  • Idiopathic thrombocytopenia (ITP)
    • Isolated thrombocytopenia without clinically apparent cause
    • Accelerated platelet destruction, often splenic sequestration
  • Evans Syndrome (pediatrics)
    • Immune thrombocytopenia (ITP) with autoimmune hemolytic anemia
    • Positive direct antiglobulin test (DAT)
  • HLA platelet refractoriness
    • Poor increment increase post platelet transfusion
    • Does not cause thrombocytopenia but will impair transfusion efforts
  • Neonatal alloimmune thrombocytopenia (NAIT) (infants)
    • Severe thrombocytopenia in infant present at birth, no thrombocytopenia in mother
    • Anti-HPA-a1 most common cause
Additional references
Board review question #1
    A 75 year old man with type II diabetes and hypertension is admitted for emergent cardiac catheterization due to an episode of chest pain with elevated cardiac enzymes. During the catheterization he requires 2 units of RBC and 1 unit of platelets for unexpected bleeding. He is stabilized and discharged after 48 hours. Six days later, he returns to his PCP with diffuse bruising and a platelet count of 9K/uL. Which item of clinical history is most pertinent to the diagnosis?

  1. The patient was taking clopidogrel
  2. The patient was in a motor vehicle accident 15 years ago, requiring multiple blood products
  3. The patient has an allergy to trimethoprim-sulfamethoxazole
  4. The patient has a sister with a history of heavy menses and easy bruising
  5. The patient’s diabetes is poorly controlled with an A1C of 12.2%
Board review answer #1
B. The patient is exhibiting post-transfusion purpura. Although this is rare and less common in males, it can occur, particularly as a patient’s comorbidities increased. Prior exposure to foreign platelet antigens, through transfusion, transplant or pregnancy can result in antihuman platelet antigen antibodies. This patient’s prior history of blood transfusion and the sudden severe thrombocytopenia (< 20K/uL) occurring 5 - 10 days after a blood transfusion is consistent with PTP. Clopidogrel is an antiplatelet medication used in patients with increased risk of cardiac events or other hypercoagulable states, it does not cause thrombocytopenia but rather a iatrogenic thrombocytopathy. Trimethoprim-sulfamethoxazole is a common culprit in drug induced thrombocytopenia. There is no evidence that this patient would have received this medication. A sister with heavy menses and easy bruising suggests vonWillebrand’s Disease (vWD). Although this is an autosomal dominant condition, even if the patient had vWD, it would not cause thrombocytopenia 5 - 10 days after a surgery. Poorly controlled diabetes can contribute to peripheral neuropathy, which can result in increased bruising or other injuries since patients do not feel the event. It does not affect the platelet count.

Reference: Post-transfusion purpura (PTP)

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Board review question #2
    A 62 year old woman is admitted for urosepsis. The clinical team calls you because they are preparing to give an RBC transfusion and might need other products as they are concerned about disseminated intravascular coagulation. They convey that the patient’s daughter insists she needs special blood because “when I was born I had low platelets and they said it was because of my mom”. You tell the clinical team that you recommend which of the following?

  1. The patient should receive leukocyte reduced RBCs as this remote pregnancy history is not currently relevant
  2. The patient should receive crossmatched platelets due to presumed HLA antibodies
  3. The patient should receive IgA deficient plasma
  4. The patient should receive washed RBCs to prevent post-transfusion purpura
  5. The patient may have an antibody and should receive phenotypically matched RBCs
Board review answer #2
D. The patient history is suggestive of neonatal alloimmune thrombocytopenia (NAIT), which is caused by antihuman platelet antigens (Most commonly Anti-HPA-1a) which cross the placenta and cause thrombocytopenia in the infant. This is also the most common Anti-HPA to be implicated in post-transfusion purpura, when a patient develops severe thrombocytopenia after a blood product transfusion. Although this patient does not have a history of post-transfusion purpura, and transfusion unmodified transfusion products could be argued for, post-transfusion purpura carries a high risk of morbidity and mortality, thus pre-emptive washing should be considered. Although HLA antibodies could be a concern in a multiparous woman, one would typically give an unmodified (other than leukocyte reduction) platelet and monitor the post-transfusion platelet count before assuming that crossmatching is needed. IgA deficient plasma is a rare, special order product that is given for patients with proven severe allergic reaction to IgA. If the patient has an antibody to a red cell antigen, that should be identified during routine type and screen. If the patients had an alloantibody that caused hemolytic disease of the fetus and newborn (HDFN), the daughter would have been born with anemia, not thrombocytopenia.

Reference: Post-transfusion purpura (PTP)

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