Hemolytic anemia

Hemolytic anemias are the geterogenous group of anemias, which characterized by shortened life span of erythrocytes in the circulation resulting from their accelerated destruction.

At the end of their normal life span (about 120 days), RBCs are removed by components of the mononuclear phagocyte system, principally in the spleen, where Hb catabolism takes place. The essential feature of hemolysis is a shortened RBC life span; hemolytic anemia results when bone marrow production can no longer compensate for the shortened RBC survival.

Classification of hemolytic anemias

Hereditary hemolytic anemias

Defects of the cell membrane:

• hereditary spherocytic anemia;

• hereditary elliptocytic anemia.

Defects of erythrocytic metabolism:

• glucose-6-phosphate dehydrogenase (G-6-PD) deficiency anemia.

Abnormal hemoglobins:

• sickle cell anemia;

• -thalassemia.

Acquired hemolytic anemia

Immunological destruction of red blood cells:

- transfusion with incompatible blood;

- hemolytic disease of the newborn;

- autoimmune hemolytic anemia (AIHA) (warm-active AIHA and cold-active AIHA).

Physical destruction of red blood cells:

-march hemoglobinuria;

• traumatic cardiac hemolytic anemia.

Hemolytic anemia induced by chemical agents.

Hemolytic anemia caused by microorganism:

• anemia of malaria;

• anemia of Clostridia.

Hemolytic anemia secondary to other disease.

Paroxysmal nocturnal hemoglobinuria.

Etiology

The causes of hemolytic anemias may be hereditary or acquired. The causes of hereditary hemolytic anemia are grouped into three categories: 1) defect of the cell membrane; 2) defects of erythrocyte metabolism; 3) abnormal hemoglobins.

Pathogenesis. Acquired hemolytic anemias have numerous causes hence corresponds with different pathogenesis. Destruction of red blood cells refers to inappropriate activation of the body's immune system and appearance either alloantibodies or autoantibodies. A number ingestion of drugs and chemicals may result to shortened life span of erythrocytes. Inflammation of blood vessels or presence of blood clots may interfere the structure and function of red blood cells and lead to early destruction. Such physical factors as vascular protheses, heart valves protheses cause accelerated hemolysis of red blood cells. Some infectious agents for example malaria parasite (Plasmodium falciparum, Clostridiax) use red blood cells for their propagation and this process destroy them. Hemolytic anemia could develop as a secondary effect of certain clinical condition such vitamin В¹² -deficiency anemia, splenomegalia, liver disease and renal failure.

Hemolysis may occur intravascularly or extravascularly. Hemoglobin liberated into the plasma is bound mainly by the alpha-2 globin, haptoglobin, to form a complex too large to be lost in the urine. It is taken up by the liver and degraded. Some hemoglobin is partially degraded and bound to albumin to form methemoglobin. If all the haptoglobin has been consumed, free hemoglobin may be lost in the urine. In small amounts this is reabsorbed by the renal tubules where the hemoglobin is degraded and the iron stored as hemosiderin. Sloughing of the renal tubular cells gives rise to hemosiderinuria which, if found, always indicates intravascular hemolysis. Hemoglobinuria occurs when greater amounts of hemoglobin are lost, giving the urine a black appearance (black water).

Extravascular hemolysis occurs in the phagocytic cells of the spleen, liver, bone marrow and other organs and there may be little or no depletion of haptoglobin.

Clinical features

Clinical features include three indications: anemia, jaundice and splenomegalia. The symptoms of anemia are common as most other one: weakness, fatigue, dyspnea, palpation, headache, dizziness, inability to concentrate. The most important sign of hemolytic anemia is jaundice, which differ from slightly yellow tint to intense lemon color of mucosa membrane, sclera and skin. Splenomegaly is specific sign, explained by hyperplasia of cells, which take part in phagocytosis. Commonly spleen is enlarged moderately.

Latent compensated hemolytic anemia explained by capacity of bone marrow to produce increased number of reticulocytes and in the peripheral circulation red blood cell counts may be fairly normal.

However the bone marrow will no longer be able to compensate and breakdown rate of erythrocytes becomes greater than the production rate of new erythrocytes. In acute cases is developed the hemolytic crisis with abrupt onset, high temperature, severe fatigue, nausea, vomiting pain in the abdomen, pronounced pallor with yellow color of mucosa and skin, hemorrhage lesions. Patient has grave condition, may be occur hemolytic coma. Tachycardia, systolic murmur, hypotension are observed. During palpation of abdomen the hepatosplenomegalia is detected.

Hemolysis may be acute, chronic, or episodic. Hemolytic crisis(acute, severe hemolysis) is uncommon; it may be accompanied by chills, fever, pain in the back and abdomen, prostration, and shock. In severe cases, hemolysis increases (jaundice, splenomegaly, and, in certain types of hemolysis, hemoglobinuria and hemosiderinuria), and erythropoiesis increases (reticulocytosis, hyperactive bone marrow). In chronic hemolysis, anemia may be exacerbated by aplastic crisis (temporary failure of erythropoiesis); this is usually related to an infection, often parvovirus.