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Thrombocytopenia

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Thrombocytopenia
SpecialtyHematology Edit this on Wikidata

Thrombocytopenia (or thrombopenia) is a relative decrease of platelets in blood.

A normal human platelet count ranges from 150,000 to 450,000 platelets per microlitre of blood.[1] These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease. One common definition of thrombocytopenia is a platelet count below 50,000 per microlitre.[2][3]

Signs and symptoms

Often, low platelet levels do not lead to clinical problems; rather, they are picked up on a routine full blood count (or CBC, complete blood count). Occasionally, there may be bruising, particularly purpura in the forearms, petechia (pinpoint hemorrhages on skin and mucous membranes), nosebleeds and/or bleeding gums.

It is vital that a full medical history is elicited to ensure the low platelet count is not due to a secondary process. It is also important to ensure that the other blood cell types, such as red blood cells and white blood cells, are not also suppressed. Painless, round and pinpoint (1 to 3 mm in diameter) petechiae usually appear and fade, and sometimes group to form ecchymoses. Larger than petechiae, ecchymoses are purple, blue or yellow-green bruises that vary in size and shape. They can occur anywhere on the body.

A person with thrombocytopenia may also complain of malaise, fatigue and general weakness (with or without accompanying blood loss). In acquired thrombocytopenia, the patient's history may include the use of one or several offending drugs.

Inspection typically reveals evidence of bleeding (petechiae or ecchymoses), along with slow, continuous bleeding from any injuries or wounds. Adults may have large, blood-filled bullae in the mouth. If the person's platelet count is between 30,000 and 50,000/mm3, bruising with minor trauma may be expected; if it is between 15,000 and 30,000/mm3, spontaneous bruising will be seen (mostly on the arms and legs).

Causes

Decreased platelet counts can be due to a number of disease processes:

Decreased production

Increased destruction

Medication-induced

Thrombocytopenia-inducing medications include:

  • Immunological platelet destruction
    • A drug molecule binds to the Fab portion of an antibody. A classic example is the quinidine group of drugs. The Fc portion of the antibody molecule is not involved in the binding process.
    • A drug molecule binds to the Fc antibody moiety, with the drug/antibody complex subsequently binding and activating the platelets. Heparin-induced thrombocytopenia (HIT) is a classic example, in which the heparin-antibody-platelet factor 4 (PF4) complex binds to the Fc receptors on the surface of the platelet. Since the Fc moiety is now unavailable to the Fc receptors of the reticulo-endothelial cells, the normally occurring destruction of the platelets is prevented. This may explain why severe thrombocytopenia is not a common feature of HIT.
    • Abciximab-induced thrombocytopenia.

More extensive lists of thrombocytopenia-inducing medications are available.[6]

Other causes

Comparing coagulation tests

Template:Bleeding worksheet

Diagnosis

Laboratory tests might include: full blood count, liver enzymes, renal function, vitamin B12 levels, folic acid levels, erythrocyte sedimentation rate, and peripheral blood smear.

If the cause for the low platelet count remains unclear, a bone marrow biopsy is usually recommended, to differentiate whether the low platelet count is due to decreased production or peripheral destruction.

Thrombocytopenia in hospitalized alcoholics may be caused by splenomegaly, folate deficiency, and, most frequently, a direct toxic effect of alcohol on production, survival time, and function of platelets. Platelet count begins to rise after 2 to 5 days' abstinence from alcohol. The condition is generally benign, and clinically significant hemorrhage is rare.

Lab tests to determine the platelet count and clotting function may also be done. In severe thrombocytopenia, a bone marrow study can determine the number, size and maturity of the megakaryocytes (the bone marrow cells that release mature platelets). This information may identify ineffective platelet production as the cause of thrombocytopenia and rule out a malignant disease process at the same time.

Treatment

Treatment is guided by etiology and disease severity. The main concept in treating thrombocytopenia is to eliminate the underlying problem, whether that means discontinuing suspected drugs that cause thrombocytopenia, or treating underlying sepsis. Diagnosis and treatment of serious thrombocytopenia is usually directed by a hematologist.

Corticosteroids may be used to increase platelet production. Lithium carbonate or folate may also be used to stimulate the bone marrow production of platelets. Platelet transfusions may be used to stop episodic abnormal bleeding caused by a low platelet count. However, if platelet destruction results from an immune disorder, platelet infusions may have only a minimal effect and may be reserved for life-threatening bleeding.

Specific treatment plans often depend on the underlying etiology of the thrombocytopenia.

Condition Treatment
Thrombotic thrombocytopenic purpura Treatment of thrombotic thrombocytopenic purpura is a medical emergency, since the hemolytic anemia and platelet activation can lead to renal failure and changes in the level of consciousness. Treatment of TTP was revolutionized in the 1980s with the application of plasmapheresis. According to the Furlan-Tsai hypothesis,[9][10] this treatment theoretically works by removing antibodies directed against the von Willebrand factor cleaving protease, ADAMTS-13. The plasmapheresis procedure also adds active ADAMTS-13 protease proteins to the patient, restoring a more physiological state of von Willebrand factor multimers. Patients with persistent antibodies against ADAMTS-13 do not always manifest TTP, and these antibodies alone are not sufficient to explain the how plasmapheresis treats TTP.
Idiopathic thrombocytopenic purpura Many cases of ITP can be left untreated, and spontaneous remission (especially in children) is not uncommon. However, counts of under 50,000 are usually monitored with regular blood tests, and those with counts of under 10,000 are usually treated, as the risk of serious spontaneous bleeding is high with a platelet count this low. Any patient experiencing severe bleeding symptoms is also usually treated. The threshold for treating ITP has decreased since the 1990s, and hematologists recognize that patients rarely spontaneously bleed with platelet counts greater than 10,000—though there are documented exceptions to this observation.

Treatments for ITP include:

Thrombopoetin analogues have been tested extensively for the treatment of ITP. These agents had previously shown promise but had been found to stimulate antibodies against endogenous thrombopoietin or lead to thrombosis.

Romiplostim (trade name Nplate, formerly AMG 531) was found to be safe and effective for the treatment of ITP in refractory patients, especially those who relapsed following splenectomy.[11][12][13]

Heparin-induced thrombocytopenia Discontinuation of heparin is critical in a case of HITT. Beyond that, however, clinicians generally treat to avoid a thrombosis, and patients started directly on warfarin after a diagnosis of HITT are at excess risk of venous limb gangrene. For this reason, patients are usually treated with a type of blood thinner called a direct thrombin inhibitor such as lepirudin or argatroban, which are approved by the U.S. Food and Drug Administration (FDA). Other blood thinners sometimes used in this setting that are not FDA-approved for treatment of HITT include bivalirudin and fondaparinux. Platelet transfusions are not a routine component of the treatment of HITT, since thrombosis, not bleeding, is the usual associated problem in this illness.
Congenital amegakaryocytic thrombocytopenia Bone Marrow/Stem Cell Transplant is the only thing that ultimately cures this genetic disease. Frequent platelet transfusions are required to keep the patient from bleeding to death until transplant is done, although this is not always the case.

Neonatal thrombocytopenia

Thrombocytopenia affects a few percent of newborns, and its prevalence in neonatal intensive care units (NICU) is high. Normally, its course is mild and it resolves without consequences. Most of the cases of thrombocytopenia affect preterm birth infants and are results of placental insufficiency and/or fetal hypoxia. The other causes are less frequent, e.g. alloimmune, genetic, autoimmune, infection, DIC.[14]

Thrombocytopenia that starts after the first 72 hours since birth is often the result of underlying sepsis or necrotising enterocolitis (NEC).[14] In the case of infection the PCR tests may be useful for rapid pathogen identification and detection of antibiotic resistance genes. The possible pathogens may be fungus, bacteria and viruses, for example: Cytomegalovirus (CMV),[14] Rubella virus,[14] HIV,[14] Staphylococcus sp.,[15] Enterococcus sp.,[15] Streptococcus agalactiae (GBS),[14] Streptococcus viridans,[16] Listeria monocytogenes,[17] Escherichia coli,[14][15] Haemophilus influenzae,[14] Klebsiella pneumoniae,[15] Pseudomonas aeruginosa,[15][18] Yersinia enterocolitica,[18] Borrelia burgdorferi,[16] Candida sp.,[15] Toxoplasma gondii.[14] The severity of thrombocytopenia might be correlated with the type of a pathogen; some research indicates that the most severe cases are related to fungal or gram-negative bacterial infection.[15] The pathogen may be transmitted during birth[19] or prior to it, but also by breast feeding.[20][21][22] or during transfusion[23][24]

The interleukin-11 is being investigated as a potential drug for aiding thrombocytopenia management, especially in the cases of sepsis or necrotising enterocolitis (NEC).[14]

Veterinary treatment

Thrombocytopenia caused by Feline Leukemia Virus and Feline immunodeficiency virus retroviral infections is treated with Lymphocyte T-Cell Immune Modulator.

References

  1. ^ "Platelet count aka thrombocyte count". Lab Tests Online UK. 2004-05-28. Retrieved 2008-05-22.
  2. ^ Correia, Maria C.B.; Domingues, Ana L.C.; Lacerda, Heloisa R.; Santos, Emília M.; MacHado, CíNtia G.F.; Hora, Viviane; Neves, Maria A.; Brito, Anelita; Coêlho, Maria R.C.D. (2009). "Platelet function and the von Willebrand factor antigen in the hepatosplenic form of schistosomiasis mansoni". Transactions of the Royal Society of Tropical Medicine and Hygiene. 103 (10): 1053–8. doi:10.1016/j.trstmh.2008.11.017. PMID 19118853.
  3. ^ Cheung, R; McAuley, R; Pollard, J (2005). "High mortality rate in patients with advanced liver disease independent of exposure to general anesthesia". Journal of Clinical Anesthesia. 17 (3): 172–6. doi:10.1016/j.jclinane.2004.06.016. PMID 15896582.
  4. ^ Scaradavou, A (2002). "HIV-related thrombocytopenia". Blood Reviews. 16 (1): 73–6. doi:10.1054/blre.2001.0188. PMID 11914001.
  5. ^ Watson, T. D; Stark, JE; Vesta, KS (2006). "Pantoprazole-Induced Thrombocytopenia". Annals of Pharmacotherapy. 40 (4): 758–61. doi:10.1345/aph.1G384. PMID 16569810.
  6. ^ "moon.ouhsc.edu".[unreliable source?]
  7. ^ Motoki, Fijita; Susumu, Yamashita; Nobukatsu, Kawamura; Ryosuke, Tsuruta; Shunji, Kasaoka; Kiyoshi, Okabayashi; Tsuyoshi, Maekawa (2005). "Viper (Agkistrodon halys blomhoffii 'Mamushi') Bite with Remarkable Thrombocytopenia". Journal of Japanese Association for Acute Medicine. 16 (3): 126–30. doi:10.3893/jjaam.16.126. ISSN 0915-924X.
  8. ^ "Onyalai".
  9. ^ Furlan, M (2001). "Aetiology and pathogenesis of thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome: the role of von Willebrand factor-cleaving protease". Best Practice & Research Clinical Haematology. 14 (2): 437–54. doi:10.1053/beha.2001.0142. PMID 11686108.
  10. ^ Tsai, H.-M. (2003). "Advances in the Pathogenesis, Diagnosis, and Treatment of Thrombotic Thrombocytopenic Purpura". Journal of the American Society of Nephrology. 14 (4): 1072–81. doi:10.1097/01.ASN.0000060805.04118.4C. PMID 12660343.
  11. ^ Bussel, James B.; Kuter, David J.; George, James N.; McMillan, Robert; Aledort, Louis M.; Conklin, George T.; Lichtin, Alan E.; Lyons, Roger M.; Nieva, Jorge (2006). "AMG 531, a Thrombopoiesis-Stimulating Protein, for Chronic ITP". New England Journal of Medicine. 355 (16): 1672–81. doi:10.1056/NEJMoa054626. PMID 17050891.
  12. ^ AMGEN (2008-03-12). "Press release: Amgen Statement on Successful Outcome of Romiplostim Panel Meeting". Business Wire via drugs.com. Retrieved 2008-05-22.
  13. ^ Richwine, Lisa (2008-03-12). "US FDA panel backs Amgen's Nplate against ITP". Reuters. Retrieved 2008-05-22.
  14. ^ a b c d e f g h i j Roberts, I; Murray, NA (2003). "Neonatal thrombocytopenia: causes and management". Archives of Disease in Childhood - Fetal and Neonatal Edition. 88 (5): F359–64. doi:10.1136/fn.88.5.F359. PMC 1721612. PMID 12937037.
  15. ^ a b c d e f g Guida, JD; Kunig, AM; Leef, KH; McKenzie, SE; Paul, DA (2003). "Platelet count and sepsis in very low birth weight neonates: is there an organism-specific response?". Pediatrics. 111 (6 Pt 1): 1411–5. PMID 12777561.
  16. ^ a b Klein, JO (1990). "Bacteriology of neonatal sepsis". The Pediatric Infectious Disease Journal. 9 (10): 778. PMID 2235163.
  17. ^ D Dzierzanowska (2001). Antybiotykoterapia praktyczna. ISBN 83-88778-20-X.[page needed]
  18. ^ a b Pacifico, L; Chiesa, C; Mirabella, S; Panero, A; Midulla, M (1987). "Early-onset Pseudomonas aeruginosa sepsis and Yersinia enterocolitica neonatal infection: a unique combination in a preterm infant". European journal of pediatrics. 146 (2): 192–3. PMID 3569360.
  19. ^ Rempen, A; Martius, J; Hartmann, AA; Wecker, I (1987). "Transmission rate of Ureaplasma urealyticum, Mycoplasma spp., Gardnerella vaginalis, B-streptococci, Candida spp. and Chlamydia trachomatis from the mother to the newborn". Archives of gynecology and obstetrics. 241 (3): 165–70. PMID 3324978.
  20. ^ Olver, WJ; Bond, DW; Boswell, TC; Watkin, SL (2000). "Neonatal group B streptococcal disease associated with infected breast milk". Archives of disease in childhood. Fetal and neonatal edition. 83 (1): F48–9. PMC 1721104. PMID 10873172.
  21. ^ Kotiw, M; Zhang, GW; Daggard, G; Reiss-Levy, E; Tapsall, JW; Numa, A (2003). "Late-onset and recurrent neonatal Group B streptococcal disease associated with breast-milk transmission". Pediatric and developmental pathology : the official journal of the Society for Pediatric Pathology and the Paediatric Pathology Society. 6 (3): 251–6. doi:10.1007/s10024-001-0276-y. PMID 12687430.
  22. ^ Gastelum, DT; Dassey, D; Mascola, L; Yasuda, LM (2005). "Transmission of community-associated methicillin-resistant Staphylococcus aureus from breast milk in the neonatal intensive care unit". The Pediatric Infectious Disease Journal. 24 (12): 1122–4. PMID 16371885.
  23. ^ Jagielski, Marek; Rastawicki, Waldemar; Kałużewski, Stanisław; Gierczyński, Rafał (2007). "Jersinioza – niedoceniana choroba zakaźna" (PDF). Przegl Epidemiol (in Polish). 56 (1): 57–64. PMID 12150068. {{cite journal}}: Unknown parameter |trans_title= ignored (|trans-title= suggested) (help)
  24. ^ Mielczarek, Paweł (2004). "Jersinioza – rzadko rozpoznawana choroba układu pokarmowego" (PDF). Prace poglądowe (in Polish). 11 (1): 69–74. {{cite journal}}: |first2= missing |last2= (help); Unknown parameter |trans_title= ignored (|trans-title= suggested) (help)

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