Thrombocytopenia (thrombocytopenia for short; D69.4- Other primary thrombocytopenia; D69.5- Secondary thrombocytopenia) occurs when the number of platelets (thrombocytes) in the blood is less than 150,000/μl (150 x 109/l).
Platelets, or thrombocytes, are solid components in the blood. They have their function in blood clotting by attaching themselves to the surrounding tissue (“platelet adhesion”) or to each other (“platelet aggregation”) when the blood vessel is injured, thus closing the injury. In addition, they release procoagulant substances in the process.
There is an increased tendency to bleed when the platelet count is below 150,000/μl. Spontaneous skin bleeding can occur at platelet counts of 30-20,000/μl and spontaneous hemorrhage at levels below 10,000/μl.
The causes of thrombocytopenia are:
- Synthesis disorders – aplastic disorders: Fanconi syndrome; bone marrow damage (chemicals – e.g., benzene -, infections (e.g., HIV); cytostatic therapy, radiation therapy).
- Bone marrow infiltrations (leukemias (blood cancers), lymphomas (cancers of the lymphatic system), bone marrow metastases/ daughter tumors in the bone marrow).
- Maturation disorders (eg, megaloblastic anemia/pernicious anemia: anemia (anemia) caused by a deficiency of vitamin B12 or, less commonly, folic acid deficiency).
- Increased peripheral turnover of platelets (e.g., idiopathic thrombocytopenic purpura (ITP; Werlhof’s disease) – autoantibody-mediated disorder of platelets; incidence: 1-4%).
Drug-induced thrombocytopenia (see under hematoxic drugs).
Platelet count < 150,000/μl should be expected in approximately 5-8% of all pregnancies. Notice: During pregnancy – predominantly in the last trimester (27th to 39th/40th week of gestation) – the platelet count physiologically drops by approximately10%.
Thrombocytopenia can be a symptom of many diseases (see under “Differential diagnoses”).
Course and prognosis: An increased bleeding tendency (hematomas (bruises), petechiae (spontaneous, punctate bleeding/flea-like bleeding of the skin and mucous membranes), nose or gum bleeding) usually leads the patient to the doctor himself.Thrombocytopenia always requires medical clarification.In the case of a low platelet count and simultaneous bleeding, acute hospitalization is required. The same applies to a platelet count < 20,000/μl (20 x 109/l) without a known diagnosis.