Hemolytic anemia is a form of anemia due to hemolysis , the abnormal breakdown of red blood cells RBCs , either in the blood vessels intravascular hemolysis or elsewhere in the human body extravascular. Symptoms of hemolytic anemia are similar to other forms of anemia fatigue and shortness of breath , but in addition, the breakdown of red cells leads to jaundice and increases the risk of particular long-term complications, such as gallstones  and pulmonary hypertension. Symptoms of hemolytic anemia are similar to the general signs of anemia. Chronic hemolysis leads to an increased excretion of bilirubin into the biliary tract , which in turn may lead to gallstones.
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At the end of their normal life span about days , red blood cells RBCs are removed from the circulation. Anemia results when bone marrow production can no longer compensate for the shortened RBC survival; this condition is termed uncompensated hemolytic anemia. If the marrow can compensate, the condition is termed compensated hemolytic anemia.
Extrinsic: From a source outside the red cell; disorders extrinsic to the RBC are usually acquired. Intrinsic: Due to an defect within the red cell; intrinsic RBC abnormalities see table Hemolytic Anemias are usually inherited. Drugs eg, quinine , quinidine , penicillins, methyldopa , ticlopidine , clopidogrel. Immunologic abnormalities eg, autoimmune hemolytic anemia , thrombotic thrombocytopenic purpura.
Mechanical injury eg, traumatic hemolytic anemia. Reticuloendothelial hyperactivity hypersplenism. Infectious organisms may cause hemolytic anemia through the direct action of toxins eg, from Clostridium perfringens , alpha- or beta-hemolytic streptococci, meningococci , by invasion and destruction of the RBC by the organism eg, Plasmodium species, Bartonella species , or by antibody production eg, Epstein-Barr virus, mycoplasma.
Defects intrinsic to the RBC that can cause hemolysis involve abnormalities of the RBC membrane, cell metabolism, or hemoglobin structure. Abnormalities include hereditary cell membrane disorders eg, hereditary spherocytosis , acquired cell membrane disorders eg, paroxysmal nocturnal hemoglobinuria , disorders of RBC metabolism eg, glucosephosphate dehydrogenase G6PD deficiency , and hemoglobinopathies eg, sickle cell disease , thalassemias.
Quantitative and functional abnormalities of certain RBC membrane proteins alpha- and beta-spectrin, protein 4. Disorder or Agent.
Disorders extrinsic to the red blood cell. Cold antibody. Hemolytic uremic syndrome. Paroxysmal cold hemoglobinuria. Thrombotic thrombocytopenic purpura. Warm antibody. Valvular heart disorders. Compounds with oxidant potential eg, dapsone , phenazopyridine. Copper Wilson disease. Intrinsic red blood cell abnormalities. Paroxysmal nocturnal hemoglobinuria.
Hereditary elliptocytosis. Hereditary spherocytosis. Hereditary stomatocytosis. Hemoglobin C disease. Hemoglobin E disease. Hemoglobin S-C disease. Sickle cell disease. Glycolytic pathway defects eg, pyruvate kinase deficiency. Hexose monophosphate shunt defects eg, glucosephosphate dehydrogenase G6PD deficiency. Senescent RBCs lose membrane and are cleared from the circulation largely by the phagocytic cells of the spleen, liver, bone marrow, and reticuloendothelial system.
Hemoglobin is broken down in these cells primarily by the heme oxygenase system. The iron is conserved and reutilized, and heme is degraded to bilirubin, which is conjugated in the liver to bilirubin glucuronide and excreted in the bile.
Most pathologic hemolysis is extravascular and occurs when damaged or abnormal RBCs are cleared from the circulation by the spleen and liver. The spleen usually contributes to hemolysis by destroying mildly abnormal RBCs or cells coated with warm antibodies. An enlarged spleen may sequester even normal RBCs. Severely abnormal RBCs or RBCs coated with cold antibodies or complement C3 are destroyed within the circulation and in the liver, which because of its large blood flow can remove damaged cells efficiently.
In extravascular hemolysis, the peripheral smear will show microspherocytes or with cold agglutinins, erythrocyte agglutination if the blood is not warmed upon collection. Intravascular hemolysis is an important reason for premature RBC destruction and usually occurs when the cell membrane has been severely damaged by any of a number of different mechanisms, including.
Disseminated intravascular coagulation DIC. With hemoglobinemia, unbound hemoglobin dimers are filtered into the urine and reabsorbed by renal tubular cells; hemoglobinuria results when reabsorptive capacity is exceeded. Iron is released from catabolized hemoglobin and embedded in hemosiderin within the tubular cells; some of the iron is assimilated for reutilization and some reaches the urine when the tubular cells slough.
Bilirubin catabolism causes increased stercobilin in the stool and urobilinogen in the urine and sometimes cholelithiasis. The bone marrow responds to the excess loss of RBCs by accelerating production and release of RBCs, resulting in a reticulocytosis due to increased production of erythropoietin by the kidneys in response to the ensuing anemia.
Systemic manifestations of hemolytic anemias resemble those of other anemias and include pallor, fatigue, dizziness, and possible hypotension. Hemolytic crisis acute, severe hemolysis is uncommon; it may be accompanied by chills, fever, pain in the back and abdomen, prostration, and shock. Hemoglobinuria causes red or reddish-brown urine. Hemolysis is suspected in patients with anemia and reticulocytosis.
The peripheral smear and reticulocyte count are the most important tests to diagnose hemolysis. Antiglobulin testing or hemoglobinopathy screening eg, high-performance liquid chromatography [HPLC] can help identify the cause of hemolysis. The peripheral smear will show schistocytes or other fragmented red cells with mechanical hemolysis. Other suggestive findings include increased levels of serum LDH and indirect bilirubin with a normal ALT, and the presence of urinary urobilinogen.
Intravascular hemolysis is suggested by RBC fragments schistocytes on the peripheral smear and by decreased serum haptoglobin levels; however, haptoglobin levels can decrease because of hepatocellular dysfunction and can increase because of systemic inflammation. Intravascular hemolysis is also suggested by urinary hemosiderin.
Urinary hemoglobin, like hematuria and myoglobinuria, produces a positive benzidine reaction on dipstick testing; it can be differentiated from hematuria by the absence of RBCs on microscopic urine examination. Free hemoglobin may make plasma reddish brown, noticeable often in centrifuged blood; myoglobin does not.
Once hemolysis has been identified, the etiology is sought. To narrow the differential diagnosis in hemolytic anemias. Most hemolytic anemias cause abnormalities in one of these variables, and so test results can direct further testing. A positive result suggests the presence of autoantibodies to RBCs.
A false-positive can occur and does not always equate with hemolysis. Thus, results should always be correlated with the clinical signs and symptoms. The indirect antiglobulin indirect Coombs test is used to detect IgG antibodies against red blood cells RBCs in a patient's plasma.
This test is also used to determine the specificity of an alloantibody. Although some tests can help differentiate intravascular from extravascular hemolysis, making the distinction is sometimes difficult. During increased RBC destruction, both types are commonly involved, although to differing degrees. RBC Morphology. Cold agglutinin disease. Glycolytic pathway defects.
Glucosephosphate dehydrogenase G6PD deficiency. Thalassemia major. Warm antibody hemolytic anemia. Hemoglobinopathies sickle cell disease , hemoglobin C disease , thalassemias. Corticosteroids are helpful in the initial treatment of warm antibody autoimmune hemolysis.
Transfusions are used in patients with symptomatic anemia, but long-term transfusion therapy may cause excessive iron accumulation, necessitating chelation therapy. Splenectomy is beneficial in some situations, particularly when splenic sequestration is the major cause of RBC destruction. If possible, splenectomy is delayed until 2 weeks after vaccination with the following:.
Pneumococcal vaccine. Haemophilus influenzae vaccine. Meningococcal vaccine. In cold agglutinin disease, avoidance of cold is recommended, and blood will need to be warmed before transfusion. Folate replacement is needed for patients with ongoing long-term hemolysis. From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world.
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Disorders extrinsic to the red blood cell Intrinsic red blood cell abnormalities. Normal red blood cell processing Extravascular hemolysis Intravascular hemolysis Consequences of hemolysis. Symptoms and Signs. Anemias Caused by Hemolysis.
Test your knowledge. Which of the following sickle cell crises occurs when marrow erythropoiesis slows during an acute infection with human parvovirus?
Overview of Hemolytic Anemia
Even though hemolytic anemias HAs are not very common, their diagnosis remains a big challenge for hematologists and clinicians. We hope that this summary will contribute with valuable information about a subject that has been little described in the medical literature, and will help to clarify the diagnostic approach to guide specific treatment depending on the causative condition. It is known that HAs are a group of disorders characterized by a premature red blood cell RBC destruction less than days , 1 , 2 that exceeds the compensatory capacity of the bone marrow to increase RBC production and keep up with the loss. Regarding the etiology, HAs can be classified as inherited or acquired and when considering the site of hemolysis, RBCs can be destroyed in the circulation intravascular or within macrophages in the spleen or liver extravascular.
Diagnostic approach to hemolytic anemias in the adult