Thrombocytopenia (synonym for thrombopenia) is a decrease in the number of platelets in the blood. There are physiological and pathological thrombocytopenia. Physiological thrombocytopenia, occurring during sleep, after eating, in the menstrual period, usually does not reach high degrees. Pathological thrombocytopenia may depend on reduced formation, increased destruction or increased consumption of platelets. Low platelet formation is observed when the hematopoietic zone narrows due to osteosclerosis, the growth of pathological tissue (for example, with leukemia), bone marrow fibrosis after exposure to ionizing radiation, and toxic lesions of the bone marrow ( uremia , benzene poisoning). Increased destruction of platelets is noted on the basis of allergy to drugs. In this case, autoimmune processes develop in which the body produces anti-platelet antibodies. Increased destruction of platelets may be due to increased activity of the spleen; its removal leads to relief of thrombocytopenia. Increased consumption of platelets is observed with extensive blood clots. A consequence of thrombocytopenia is a tendency to bleed. The most prominent manifestation of thrombocytopenia is thrombocytopenic purpura (see).