Name = Thrombocytopenia
DiseasesDB = 27522
ICD10 = ICD10|D|69|6|d|65, ICD10|P|61|0|p|50
ICD9 = ICD9|287.3, ICD9|287.4, ICD9|287.5
OMIM = 188000
OMIM_mult = OMIM2|313900
MedlinePlus = 000586
MeshID = D013921
Thrombocytopenia (or -paenia, or thrombopenia in short) is the presence of relatively few
Generally speaking, in humans, a normal platelet count ranges from 150,000 and 450,000 per mm3 (microlitre).Cite web
title=Platelet count aka thrombocyte count
Lab Tests Online UK
date=2004-05-28] These limits, however, are determined by the 2.5th lower and upper
percentile, and a deviation does not necessarily imply any form of disease. The number of platelets in a blood sample also decreases rather quickly with time and a low platelet count may be caused by a delay between sampling and analysis.
igns 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 purpurain the forearms, 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
red blood cells, and white blood cells, are not also suppressed.
Laboratory tests might include:
full blood count, liver enzymes, renal function, vitamin B12levels, folic acidlevels, erythrocyte sedimentation rate, and peripheral blood smear.
If the cause for the low platelet count remains unclear,
bone marrow biopsyis often undertaken, to differentiate whether the low platelet count is due to "decreased production" or "peripheral destruction".
Decreased platelet counts can be due to a number of disease processes:
vitamin B12or folic aciddeficiency
leukemiaor myelodysplastic syndrome
**Decreased production of
thrombopoietinby the liverin liver failure.
Sepsis, systemic viralor bacterial infection
Dengue fevercan cause thrombocytopenia by direct infection of bone marrow megakaryocytesas well as immunological shortened plateletsurvival
Congenital Amegakaryocytic Thrombocytopenia (CAMT)
Thrombocytopenia absent radiussyndrome
Bernard-Soulier syndrome, associated with large platelets
May-Hegglinanomaly, the combination of thrombocytopenia, pale-blue leuckocyte inclusions, and giant platelets
Grey platelet syndrome
idiopathic thrombocytopenic purpura(ITP)
thrombotic thrombocytopenic purpura(TTP)
disseminated intravascular coagulation(DIC)
paroxysmal nocturnal hemoglobinuria(PNH)
systemic lupus erythematosus(SLE)
post transfusion purpura
neonatal alloimmune thrombocytopenia(NAITP)
**Splenic sequestration of platelets due to
Dengue feverhas been shown to cause shortened platelet survival and immunological platelet destruction
**HIV cite journal |author=Scaradavou A |title=HIV-related thrombocytopenia |journal=Blood Rev. |volume=16 |issue=1 |pages=73–6 |year=2002 |pmid=11914001 |doi=10.1054/blre.2001.0188 |url=http://linkinghub.elsevier.com/retrieve/pii/S0268960X01901882
The most comprehensive list of thrombocytopenia-inducing medications is maintained by Dr. James George at Ohio State University [http://moon.ouhsc.edu/jgeorge/drug%20ITP_single04.htm at this website, though last updated in 2004] . A small subset of drug-induced thrombocytopenia culprits:
**Other chemotherapy drugs
*Immunological platelet destruction
**Drug binds Fab portion of an
antibody. The classic example of this mechanism is the quinidinegroup of drugs. The Fc portion of the antibody molecule is not involved in the binding process.
**Drug binds to Fc, and drug-antibody complex binds and activates platelets.
Heparin induced thrombocytopenia(HIT) is the classic example of this phenomenon. In HIT, the heparin-antibody-platelet factor 4 (PF4) complex binds to Fc receptors on the surface of the platelet. Since Fc portion of the antibody is bound to the platelets, they are not available to the Fc receptors of the reticulo-endothelial cells, so therefore this system cannot destroy platelets as usual. This may explain why severe thrombocytopenia is not a common feature of HIT.
Heparin-induced thrombocytopenia(HIT or "white clot syndrome"): this is a rare but serious condition that may occur in a hospitalized population. The most common clinical setting for HIT is in postoperative coronary artery bypass graft recipients, who may receive large quantities of heparin during surgery. HIT typically occurs about a week after exposure to heparin. The heparin-PF4 antibody complex will activate the platelets, and this can often lead to thrombosis. The term HITT, where the last T stands for thrombosis, denotes the concept that heparin-induced thrombocytopenia often is associated with thrombosis.
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
Specific treatment plans often depend on the underlying
etiologyof the thrombocytopenia.
Thrombotic thrombocytopenic purpura (TTP)
thrombotic thrombocytopenic purpurais a medical emergency, since the hemolytic anemiaand platelet activation can lead to renal failureand 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[cite journal |author=Furlan M, Lämmle B |title=Aetiology and pathogenesis of thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome: the role of von Willebrand factor-cleaving protease |journal=Best Pract Res Clin Haematol |volume=14 |issue=2 |pages=437–54 |year=2001 |pmid=11686108 |doi=10.1053/beha.2001.0142] [cite journal |author=Tsai H |title=Advances in the pathogenesis, diagnosis, and treatment of thrombotic thrombocytopenic purpura |journal=J Am Soc Nephrol |volume=14 |issue=4 |pages=1072–81 |year=2003 |pmid=12660343 |doi=10.1097/01.ASN.0000060805.04118.4C] , this treatment theoretically works by removing antibodiesdirected against the von Willebrand factorcleaving protease, ADAMTS-13. The plasmapheresis procedure also adds active ADAMTS-13 protease proteinsto 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 (ITP)
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 monitiored 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 bleed with platelet counts greater than ten thousand, though there are documented exceptions to this observation. Treatments for ITP include:
Prednisoneand other corticosteroids
Intravenous Immune globulin
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
thrombopoeitinor lead to thrombosis.
A investigational medication known as
AMG 531( Romiplostim, trade name Nplate) was found, in early studies, to be safe and effective for the treatment of ITP in refractory patients. [cite journal |author=Bussel J, Kuter D, George J, McMillan R, Aledort L, Conklin G, Lichtin A, Lyons R, Nieva J, Wasser J, Wiznitzer I, Kelly R, Chen C, Nichol J |title=AMG 531, a thrombopoiesis-stimulating protein, for chronic ITP |journal=N Engl J Med |volume=355 |issue=16 |pages=1672–81 |year=2006 |pmid=17050891 |doi=10.1056/NEJMoa054626] [Cite news
Business Wirevia drugs.com
title=Press release: Amgen Statement on Successful Outcome of Romiplostim Panel Meeting
url=http://www.drugs.com/nda/romiplostim_080313.html] [Cite news
title=US FDA panel backs Amgen's Nplate against ITP
url=http://www.reuters.com/article/rbssHealthcareNews/idUSWAT00911720080312] AMG 531 is a
peptidethat bears no sequence homologywith endogenous human thrombopoeitin, so it is not as likely to lead to neutralizing antibodies as previous peptide thrombopoeitinanalogues. [cite journal |author=Broudy V, Lin N |title=AMG531 stimulates megakaryopoiesis in vitro by binding to Mpl |journal=Cytokine |volume=25 |issue=2 |pages=52–60 |year=2004 |pmid=14693160 |doi=10.1016/j.cyto.2003.05.001]
Heparin-induced thrombocytopenia and thrombosis (HITT)
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
warfarinafter a diagnosis of HITT are at excess risk of venous limb gangrene. For this reason, patients are usually treated with a type of blood thinnercalled a direct thrombin inhibitorsuch as the FDA-approved lepirudinor argatroban. Other blood thinnerssometimes used in this setting that are not FDA-approved for treatment of HITT include bivalirudinand fondaparinux. Platelet transfusionsare not a routine component of the treatment of HITT, since thrombosis, not bleeding, is the usual associated problem in this illness.
Congenital amegakaryocytic thrombocytopenia (CAMT)
Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare
inheriteddisorder. The primary manifestations are thrombocytopeniaand megakaryocytopenia, or low numbers of platelets and megakaryocytes. There is an absence of megakaryocytes in the bone marrow with no associated physical abnormalities.cite journal | author=Freedman MH, Estrov Z| title= Congenital amegakaryocytic thrombocytopenia: an intrinsic hematopoietic stem cell defect | date=1990 |journal=Am. J. Pediatr. Hematol. Oncol. |volume=12 | pages=225–230] The cause for this disorder appears to be a mutation in the gene for the TPO receptor, "c-mpl", despite high levels of serum TPO.cite journal | author=Ihara K, Ishii E, Eguchi M, Takada H, Suminoe A, Good RA, Hara T |title=Identification of mutations in the c-mpl gene in congenital amegakaryocytic thrombocytopenia |journal=Proc. Natl. Acad. Sci. |date=1999 |volume=96 |pages=3133–6 | doi=10.1073/pnas.96.6.3132 |pmid=10077649] cite journal | author=Ballmaier M, Germeshausen M, Schulze H, Cherkaoui K, Lang S, Gaudig A, Krukemeier S, Eilers M, Strauss G, Welte K | title=C-mpl mutations are the cause of congenital amegakaryocytic thrombocytopenia |journal=Blood. |date=2001 |volume=97|pages=139–46 | doi=10.1182/blood.V97.1.139 | pmid=11133753] In addition, there may be abnormalities with the central nervous systemincluding the cerebrumand cerebellumwhich could cause symptoms. The primary treatment for CAMT is bone marrow transplantation.
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.
One of the few non Medical Research related sources on the web with some information on CAMT is;
* [http://www.haleysgiggle.com/ CAMT Specific Infant Bone Marrow Transplant Journal]
There appears to be no generic resource for CAMT patients on the web, and this is potentially due to the rariety of the disease.
* [http://www.thrombocytopenia.info Thrombocytopenia Forum]
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