Pale nose color is one of the symptoms of anemia. Anemia is a pathological condition in which the amount of hemoglobin, red blood cell count and red blood cell pressure volume per unit volume of circulating blood is lower than normal. According to the cause, anemia can be divided into three major categories: hematopoietic dysplasia, hemorrhagic and hemolytic. I. Hematopoietic anemia (decreased erythropoiesis) (a) Hemoglobin synthesis disorder 1. Iron deficiency anemia: insufficient iron intake, relatively increased iron requirement (pregnancy, children’s growth and development period) iron absorption disorder (chronic gastrointestinal diseases, after major gastrectomy), chronic blood loss. 2, iron granulocytic anemia. 3, Vitamin B6 reactive anemia. 4.Carboxyferrin deficiency anemia. (II) Nuclear maturation disorder 1, pernicious anemia. 2.Megaloblastic anemia caused by other causes of folic acid and vitamin Bl2 deficiency: malnutrition (lack of food, improper feeding of infants and children, chronic alcoholism, persistent anorexia), increased need (pregnancy, lactation, growth and development of children, broad-joint tapeworm infection, hemolysis, infection, hyperthyroidism, etc.), malabsorption (after total or partial gastrectomy, chronic atrophic gastritis, gastric cancer, chronic liver disease, chronic enteritis, malabsorption syndrome, post-intestinal resection, bacterial infection of intestinal diverticulum), the effect of drugs on nucleic acid metabolism (such as anti-folate agents, anticonvulsants, anti-tuberculosis drugs, oral contraceptives, neomycin, nitrites, etc.). (C) Bone marrow hypoplasia 1. Stem cell defects (1) Aplastic anemia. (2) Congenital aplastic anemia. (3) Pure red blood cell aplastic anemia. (4) Myelodysplastic syndrome. 2.Bone marrow hematopoietic tissue is crowded by other cells Leukemia, malignant lymphoma, multiple myeloma, metastatic cancer of bone marrow, myelofibrosis, systemic mastocytosis, marble bone disease, etc. 3. Defective erythropoietic regulators Renal anemia, endocrine gland (e.g. pituitary, thyroid) hypofunction, infectious anemia, etc. Hemorrhagic anemia (a) Acute hemorrhagic anemia such as trauma causing massive external bleeding or rupture of internal organs, ectopic pregnancy, gastrointestinal hemorrhage, etc. (2) Chronic blood loss anemia such as excessive menstruation, hemorrhoid bleeding, hookworm disease, stomach cancer, peptic ulcer, etc. (3) Hemolytic anemia (excessive destruction of red blood cells) (1) Intrinsic defects of red blood cells 1. Congenital heredity (1) Abnormal red blood cell membrane: hereditary spherocytosis, hereditary elliptocytosis, hereditary stomatocytosis. (2) Erythrocyte enzyme abnormalities: defects in enzymes in sugar anaerobic enzymes (e.g. pyruvate kinase deficiency) deficiencies in enzymes in the phosphate hexose bypass (~ phosphoglucose dehydrogenase deficiency, often induced by taking oxidizing drugs such as fava beans and primaquine or by infection; hemolytic anemia due to deficiencies in other related components). (3) Abnormalities of peptide chains: abnormalities in the amount of peptide chains (Q-thalassemia, B-thalassemia), abnormalities in the structure of peptide chains (polymeric hemoglobinopathy, unstable hemoglobinopathy). 2. Acquired Acquired Paroxysmal sleep hemoglobinuria (PNH) (ii) Extrinsic red blood cell factors 1. Immune (1) Autoimmune: warm antibody type (acute idiopathic acquired hemolytic anemia, chronic idiopathic warm antibody immune hemolytic anemia, symptomatic warm antibody immune hemolytic anemia) cold antibody type (idiopathic chronic cold agglutinin disease, paroxysmal cold hemoglobinuria, symptomatic cold agglutinin patients). (2) Alloimmune: neonatal hemolytic disease, ABO blood group incompatibility hemolytic transfusion reaction, Rh blood group incompatibility hemolytic transfusion reaction. (3) Drug-immune hemolytic anemia: seen in para-aminosalicylic acid, isoniazid, rifampin, quinidine, finasteride, aminopyrine, sulfonamides, chlorpromazine, chlorosulfonylurea, insulin, penicillin, cephalosporin, etc. 2. Non-immune (1) Mechanical factors (red blood cell fragmentation syndrome): microangiopathic hemolytic anemia and hemolytic anemia after prosthetic heart valve replacement. (2) Infectious hemolytic anemia: malaria, sepsis, etc. (3) Hemolytic anemia due to biological factors; snake venom, poisonous mushrooms, etc. (4) Hemolytic anemia caused by drugs and chemicals. (5) Hypersplenism. (6) Disseminated intravascular coagulation (DIC). (7) Ionizing radiation.