Seventeen thousand platelets refers to a platelet index of 17×10⁹/L, indicating thrombocytopenia. The causes of thrombocytopenia include primary immune thrombocytopenia, aplastic anemia, drug-induced, and malignant hematologic diseases. 1. Primary immune thrombocytopenia: it is related to autoimmune abnormality, the body produces anti-platelet antibodies and combines them with platelets, and the platelets combined with the antibodies are phagocytosed by macrophages, thus causing thrombocytopenia. 2. Aplastic anemia: the main manifestation is anemia, which may be accompanied by bleeding tendency caused by thrombocytopenia. Severe remittent syndrome, the onset of disease is rapid, rapid progress, often with bleeding and infection and fever as the first and main manifestations. Non-severe cataracts, slow onset, anemia as the first and main manifestations, bleeding is mostly limited to the skin and mucous membranes, can be complicated by infection. 3. Drug-induced: the application of quinidine, sulfonamide, digitalis glycosides and other drugs will lead to thrombocytopenia, accompanied by chills, fever, headache and other systemic manifestations. 4. Malignant hematologic diseases: such as leukemia, myelodysplastic syndromes, etc., platelet index will also be reduced. Platelet 17×10⁹/L may also have other causes, it is recommended to go to the hospital in time to identify the causes, under the guidance of the physician early formal treatment.