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).


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
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