Figure shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-section of a normal red blood cell with normal hemoglobin. The causes of<unk>  may be classified as impaired red blood cell (RBC) production, increased RBC destruction (hemolytic<unk> , blood loss and fluid overload (hypervolemia). Several of these may interplay to cause<unk> . The most common cause of<unk>  is blood loss, but this usually does not cause any lasting symptoms unless a relatively impaired RBC production develops, in turn, most commonly by iron deficiency. Impaired production * Disturbance of proliferation and differentiation of stem cells * Pure red cell aplasia * Aplastic<unk>  affects all kinds of blood cells. Fanconi<unk>  is a hereditary disorder or defect featuring aplastic<unk>  and various other abnormalities. *<unk>  of kidney failure due to insufficient production of the hormone erythropoietin *<unk>  of endocrine disease * Disturbance of proliferation and maturation of erythroblasts * Pernicious<unk>  is a form of megaloblastic<unk>  due to vitamin B12 deficiency dependent on impaired absorption of vitamin B12. Lack of dietary B12 causes non-pernicious megaloblastic<unk> . *<unk>  of folate deficiency, as with vitamin B12, causes megaloblastic<unk>  *<unk>  of prematurity, by diminished erythropoietin response to declining hematocrit levels, combined with blood loss from laboratory testing, generally occurs in premature infants at two to six weeks of age. * Iron deficiency<unk> , resulting in deficient heme synthesis * Thalassemias, causing deficient globin synthesis * Congenital dyserythropoietic<unk> s, causing ineffective erythropoiesis *<unk>  of kidney failure (also causing stem cell dysfunction) * Other mechanisms of impaired RBC production * Myelophthisic<unk>  or myelophthisis is a severe type of<unk>  resulting from the replacement of bone marrow by other materials, such as malignant tumors, fibrosis, or granulomas. * Myelodysplastic syndrome *<unk>  of chronic inflammation * Leukoerythroblastic<unk>  is caused by space-occupying lesions in the bone marrow that prevent normal production of blood cells. Increased destruction<unk> s of increased red blood cell destruction are generally classified as hemolytic<unk> s. These types generally feature jaundice, and elevated levels of lactate dehydrogenase. * Intrinsic (intracorpuscular) abnormalities cause premature destruction. All of these, except paroxysmal nocturnal hemoglobinuria, are hereditary genetic disorders. * Hereditary spherocytosis is a hereditary defect that results in defects in the RBC cell membrane, causing the erythrocytes to be sequestered and destroyed by the spleen. * Hereditary elliptocytosis is another defect in membrane skeleton proteins. * Abetalipoproteinemia, causing defects in membrane lipids * Enzyme deficiencies * Pyruvate kinase and hexokinase deficiencies, causing defect glycolysis * Glucose-6-phosphate dehydrogenase deficiency and glutathione synthetase deficiency, causing increased oxidative stress * Hemoglobinopathies * Sickle cell<unk>  * Hemoglobinopathies causing unstable hemoglobins * Paroxysmal nocturnal hemoglobinuria * Extrinsic (extracorpuscular) abnormalities * Antibody-mediated * Warm autoimmune hemolytic<unk>  is caused by autoimmune attack against red blood cells, primarily by IgG. It is the most common of the autoimmune hemolytic diseases. It can be idiopathic, that is, without any known cause, drug-associated or secondary to another disease such as systemic lupus erythematosus, or a malignancy, such as chronic lymphocytic leukemia. * Cold agglutinin hemolytic<unk>  is primarily mediated by IgM. It can be idiopathic or result from an underlying condition. * Rh disease, one of the causes of hemolytic disease of the newborn * Transfusion reaction to blood transfusions * Mechanical trauma to red blood cells * Microangiopathic hemolytic<unk> s, including thrombotic thrombocytopenic purpura and disseminated intravascular coagulation * Infections, including malaria * Heart surgery * Haemodialysis * Parasitic * Trypanosoma congolense alters the surfaces of RBCs of its host and this may explain T. c. induced<unk>  Blood loss *<unk>  of prematurity, from frequent blood sampling for laboratory testing, combined with insufficient RBC production * Trauma or surgery, causing acute blood loss * Gastrointestinal tract lesions, causing either acute bleeds (e.g. variceal lesions, peptic ulcers) or chronic blood loss (e.g. angiodysplasia) * Gynecologic disturbances, also generally causing chronic blood loss * From menstruation, mostly among young women or older women who have fibroids * Many type of cancers, including colorectal cancer and cancer of the urinary bladder, may cause acute or chronic blood loss, especially at advanced stages * Infection by intestinal nematodes feeding on blood, such as hookworms and the whipworm Trichuris trichiura * Iatrogenic<unk> , blood loss from repeated blood draws and medical procedures. The roots of the words<unk>  and ischemia both refer to the basic idea of "lack of blood", but<unk>  and ischemia are not the same thing in modern medical terminology. The word<unk>  used alone implies widespread effects from blood that either is too scarce (e.g., blood loss) or is dysfunctional in its oxygen-supplying ability (due to whatever type of hemoglobin or erythrocyte problem). In contrast, the word ischemia refers solely to the lack of blood (poor perfusion). Thus ischemia in a body part can cause localized<unk>  effects within those tissues. Fluid overload Fluid overload (hypervolemia) causes decreased hemoglobin concentration and apparent<unk> : * General causes of hypervolemia include excessive sodium or fluid intake, sodium or water retention and fluid shift into the intravascular space. * From the 6th week of pregnancy, hormonal changes cause an increase in the mother's blood volume due to an increase in plasma. Intestinal inflammation Certain gastrointestinal disorders can cause<unk> . The mechanisms involved are multifactorial and not limited to malabsorption but mainly related to chronic intestinal inflammation, which causes dysregulation of hepcidin that leads to decreased access of iron to the circulation. * Helicobacter pylori infection. * Gluten-related disorders: untreated celiac disease and non-celiac gluten sensitivity.<unk>  can be the only manifestation of celiac disease, in absence of gastrointestinal or any other symptoms. * Inflammatory bowel disease.
Anemia
Heart failure
Analbuminaemia
Narcolepsy
Pancytopenia
Basopenia
Osteopenia
Leukopenia