Immune Thrombocytopenia (ITP)


Immune thrombocytopenia (ITP) is a disease that results in rapid, immune-mediated platelet destruction and the suppression of platelet production. ITP can manifest as a primary disorder or as a secondary condition when it coexists with other concomitant disorders.1

Immune thrombocytopenia is a diagnosis of exclusion that shows isolated thrombocytopenia with a peripheral blood platelet count of <100×109/L with no anemia or leukopenia and no apparent cause of thrombocytopenia.2 

It is important to rule out other potential causes of low platelet count and associated bleeding. Peripheral blood counts and blood smear are mandatory to assess platelet levels.3 In rare cases, such as vague diagnosis, nonresponse to standard treatments, or abnormalities besides thrombocytopenia on blood tests, the examination of bone marrow aspiration smears and bone marrow biopsies is required.4

Splenectomy is not favored as an initial treatment for adults or option for children. However, it does achieve a high response rate for clinical remission.5 Indications for splenectomy in patients with ITP include severe menorrhagia, life-threatening hemorrhage, lifestyle limitations due to the disease, and chronic, refractory cases that have not responded to multiple other treatment options.6 Because the spleen serves as the main organ of immunological response to bloodborne antigens, it is the primary site of ITP pathogenesis. Its removal often delivers rapid and complete remission from disease.5

Read more about ITP surgical management

Bone Marrow Aspirate and Biopsy

Bone marrow aspirates from patients with ITP show normal cellularity with normal morphological appearances of erythroid and myeloid precursors. The number of megakaryocytes may be increased, and these hematopoietic cells may seem immature or large due to a decrease in peripheral platelets, yet morphology may be normal. If the bone marrow aspirate is from older patients, this morphology should be carefully examined to exclude the onset of myelodysplastic syndrome.7 

Other findings that have been reported in megakaryocytes include megakaryocytic hyperplasia with nongranular pseudoplatelet formation, a smooth nonbudding cellular membrane, increased numbers of immature megakaryocytes, reduced granularity and platelet production, degenerative changes, reduced ploidy, and more numerous and larger forms.1 

Bone marrow biopsy is not required to make a diagnosis of ITP. However, it is recommended in patients with relapsed or refractory disease before initiating second-line therapy.8 Histological studies of bone marrow biopsy specimens or marrow clots show normal to increased numbers of megakaryocytes with no other significant findings. Signs of increased marrow fibrosis and hypoplasia are absent. For a diagnosis of ITP, the value of bone marrow examination is still subject to debate, and additional studies are required to create definitive standards.7,9 

Read more about ITP testing

Spleen Histology

Histological findings are nonspecific in splenectomy specimens from ITP cases. However, resected spleens must be thoroughly screened for primary splenic lymphoma, granuloma, or other findings of an unidentified infectious condition.7

Histological sections from the spleen may show prominent white pulp with focal germinal centers and hyperplasia of marginal zones. The red pulp is cellular, containing histiocytes, lymphocytes that have been activated (immunoblasts), neutrophils, and an increase in the number of cordal macrophages, which phagocytose platelets that are coated in antibodies. Due to granular platelet debris both inside macrophages and extracellularly, cords of Billroth can show a dirty appearance.2 

Read more about ITP pathophysiology

References

  1. Gunduz E, Kivanc BK, Arik D, İsiksoy S, Bal C, Akay OM. Bone marrow examination in patients with immune thrombocytopenia: is there anything different in older patients? Eur J Haematol. 2014;93(2):157-160. doi:10.1111/ejh.12320
  2. Kapur R. Immune thrombocytopenia (ITP). PathologyOutlines.com. Updated April 2, 2021. Accessed October 31, 2022.
  3. Immune thrombocytopenia (ITP): diagnosis and treatment. Mayo Clinic. February 25, 2021. Accessed October 31, 2022. 
  4. Zainal A, Salama A, Alweis R. Immune thrombocytopenic purpura. J Community Hosp Intern Med Perspect. 2019;9(1):59-61. doi:10.1080/20009666.2019.1565884
  5. Geyer JT, Bussel JB. The spleen in immune thrombocytopenia. Hemasphere. 2018;2:169-172. doi:10.1097/HS9.0000000000000116
  6. Warrier R, Chauhan A. Management of immune thrombocytopenic purpura: an update. Ochsner J. 2012;12(3):221-227. 
  7. Kessler CM. Immune thrombocytopenia (ITP) workup. Medscape. Updated January 7, 2021. Accessed October 31, 2022.
  8. Agnelli Giacchello J, Godio L, Dainese C, Valeri F, Boccadoro M, Borchiellini A. Megakaryocytic hyperplasia in bone marrow biopsy as a novel predictor of response in patients with immune thrombocytopenia. Abstract presented at: International Society on Thrombosis and Haemostasis (ISTH) 2020 Congress; July 12-14, 2020; Virtual.
  9. Immune thrombocytopenia. The Royal College of Pathologists of Australasia (RCPA). Accessed November 1, 2022.

Reviewed by Hasan Avcu, MD, on 10/31/2022.

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