Mr. Yuan, 42 years old, suddenly felt dizzy, weak, and had blood in his urine for several days in a row. He was examined in the hematology department of the hospital. “At that time, the patient came with a shriveled face. After routine hematological examination the hematocrit was only 38 g/L, which was far below the standard for normal people (120-160 g/L). A chest CT did not reveal a thymoma. The bone marrow examination suggested pure red blood cell aplastic anemia.” Mr. Yuan felt puzzled, he had been in good health, how could he suddenly become anemic? Dr. Kuang-Hua Yan inquired about Mr. Yuan’s medical history in detail and found that Mr. Yuan had been in a car accident 1 month ago and had undergone a right temporal top craniotomy to remove the hematoma. After the operation, in order to prevent the occurrence of epilepsy, the doctor prescribed him phenytoin sodium tablets (0.1g once, 3 times a day). When he came to see the doctor at the First Affiliated Hospital of the University of Heilongjiang, Mr. Yuan had been taking the drug for more than 20 days. Considering that Mr. Yuan’s anemia might be caused by phenytoin sodium, the patient was immediately instructed to stop taking the drug, and the patient was treated, and the indicators were normal on recheck after 3 weeks. It is understood that pure red blood cell aplastic anemia (referred to as pure red reblast) is a relatively rare type of anemia. It is characterized by significant anemia, but normal white blood cells and platelets. It can be divided into congenital and acquired, with acquired being the majority, and acquired can be divided into primary and secondary. The majority of primary cases are autoimmune diseases, with a few cases of unknown etiology. Secondary causes include thymoma, infections, drugs, chemicals, hemolytic anemia, systemic lupus erythematosus, rheumatoid arthritis, and acute renal failure. In addition to pure red remittance, which can be caused by the antiepileptic drugs phenytoin sodium and phenobarbital, the anti-tuberculosis drug isoniazid, the antibiotic chloramphenicol, and the antipyretic drugs acetaminophen and aminopyrine can also cause it. Therefore, the causes of anemia can be so varied that taking medication can also cause anemia, and we should not take medication at our own discretion.