Definition
Thrombocytopenia is present if the platelet count decreases below
x 109/L. Before the diagnosis of thrombocytopenia can be established, pseudo-thrombocytopenia must always be excluded.
Clinical picture:
Thrombocytopenia usually causes spontaneous bleeding at values under 20 x 109/L, providing that no additional platelet defect is present. Skin and mucous membrane bleeding are typical (petechiae and ecchymoses).
Occurrence:
Thrombocytopenia can be etiologically subdivided into four groups.
| 1. Decreased production | a) General bone marrow insufficiency: - Leukemia - Myelodysplastic syndromes - Myelofibrosis - Megaloblastic anemia - Bone marrow infiltration by lymphoma or solid tumor metastases b) Selective megakaryocytic hypoplasia - Drugs, alcohol, chemicals - Radiation exposure - Viral infections c) Inherited - May-Hegglin anomaly - Wiskott-Aldrich syndrome - Bernard-Soulier syndrome and others |
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2. Shortened survival span
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a) Immunologic - Autoantibodies (ITP, CLL, connective tissue diseases, e.g. lupus erythematosus, HIV) - Alloantibodies (after transfusions, neonatal) b) Drug-induced c) Microangiopathic hemolytic anemia - TTP, hemolytic-uremic syndrome (HUS), disseminated intravascular coagulation (DIC) |
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3. Sequestration
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Various causes of splenomegaly, e.g. congestive splenomegaly in portal hypertension |
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4. Hemodilution
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After massive blood transfusion |