Thrombocytopenia

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Thrombocytopenia
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Checkpoint Primary Hemostasis

• Its about vasculature
• Its about platelets
• Its about maintaining blood in a fluid state
  within the blood vessels and preventing excessive
  blood loss after vascular injury
• Bottomline
• Platelet Abnormalities
• QUANTITAIVE OR QUALITATIVE result in bleeding

Graphic accessed URL http//www.uv.es/vicalegr/CL
index/CLvasculitis/vasleu11.jpg , 2005.
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Clinical ManifestationsPrimary v.s. Secondary
Disorders of Hemostasis

• Primary
• Skin
• petechiae
• purpura
• ecchymoses
• Mucous membranes
• nose bleeds
• sclera
• gums

• Secondary
• Tissues
• Joints

http//heme-coag.uthscsa.edu/wwwbleed97/22apet.gif
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Platelet-Associated Disorders

• Quantitative Numbers game
• Increased thrombocytosis
• gt450,000/ml
• Decreased thrombocytopenia
• lt150,000/ml

http//www.mcl.tulane.edu/classware/pathology/Krau
se/ET/RM1.html
http//lifesci.rutgers.edu/babiarz/Histo/Blood/Sm
ear2.jpg
http//www.ispub.com/xml/journals/ijid/vol3n2/viva
x-fig1.jpg
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Thrombocytopenia Definition

• Thrombocytopenia is defined as a platelet count
  less than 150,000
• 2.5 percent of the normal population will have a
  platelet count lower than this

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Bleeding

• Surgical bleeding less than 50,000
• Spontaneous bleeding less than 10,000 to 20,000
• Severe life threatening bleeding less than 6000

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Thrombocytopenia
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Differential

• Pseudothrombocytopenia
• Decreased Production- suggested by
• other cytopenias
• normal sized/small platelets suggest a reduced
  bone marrow response to need
• Increased Destruction- suggested by
• Microangiopathic blood picture (fragmented RBCs,
  high LDH)
• Large platelets on smear
• Associated autoimmune disease

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Pseudothrombocytopenia

• If blood sample is inadequately anticoagulated,
  platelet clumps can be counted as WBCs
• 0.1 of patients have EDTA dependent agglutinins
  leading to platelet clumping and
  pseudothrombocytopenia
• Can also be seen after administration of
  abciximab
• If platelet clumping is observed, repeat the
  count using heparin or citrate as anticoagulant

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Decreased platelet production

• In almost all disorders caused by marrow
  suppression or damage, white cell and red cell
  production are also affected.
• Viral infections- rubella, mumps, varicella,
  parvovirus, hepatitis C, EBV
• Direct megakaryocyte damage-HIV
• Post chemotherapy or radiation therapy
• Acquired bone marrow hypoplasia- Fanconi anemia,
  acquired pure megakaryocytic aplasia
• Direct alcohol toxicity
• B12 or folate deficiency

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Increased Platelet destruction

• ITP and SLE- mechanism presumed to be presence
  of autoimmune anti-platelet Abs
• Alloimmune destruction- posttransfusion, post-
  transplantation
• Hypersplenism
• Disseminated intravascular coagulation
• TTP- HUS
• HELLP in pregnant women
• Medications- heparin, quinine, valproic acid
• Infections- EBV, CMV, sepsis
• Physical destruction during cardiopulmonary
  bypass, intravascular or intracardiac metastatic
  lesions

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Pathophysiology of ITP
O
Autoantibody Production
AP
Platelet Opsonization
O
Platelet Destruction
D
AP
D
Platelet Production
P
T-CellMediated Cytotoxicity
TC
P
TC
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Diagnosis

• Repeat lab
• Peripheral smear
• Coagulation study
• Fibrinogen, d-dimer
• ITP- presumptive diagnosis if history, physical
  examination, complete blood count, and
  examination of the peripheral blood smear do not
  suggest other etiologies.
• Bone marrow biopsy- unexplained thrombocytopenia
  severe enough to constitute a risk for major
  bleeding

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History

• Recent viral or rickettsial infection
• Previously diagnosed hematologic disease
• Nonhematologic diseases known to decrease
  platelet counts (eg, eclampsia, sepsis, DIC,
  anaphylactic shock, hypothermia, massive
  transfusions)
• A positive family history of bleeding and/or
  thrombocytopenia
• Recent live virus vaccination
• Poor nutritional status, especially in the
  elderly and alcoholics
• Medications
• Pregnancy, especially late in the third trimester
  or at onset of labor
• Recent organ transplantation from a donor
  sensitized to platelet alloantigens
• Recent transfusion of a platelet-containing
  product in an allosensitized recipient

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Physical exam

• Petechiae pinhead sized, red, flat, discrete
  lesions often occurring in crops in dependent
  areas
• Purpura purplish discoloration of the skin due
  to the presence of confluent petechiae.
• Ecchymoses nontender areas of bleeding into the
  skin, usually associated with multiple colors,
  due to the presence of extravasated blood