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 syndrome - 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 |
|---|---|
|
2. Shortened survival span
|
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) |
|
3. Sequestration
|
Various causes of splenomegaly, e.g. congestive splenomegaly in portal hypertension |
|
4. Hemodilution
|
After massive blood transfusion |