Hemolytic anemia

Hemolytic anemia is defined as the destruction of red blood cells (RBCs) before their normal 120-day life span. While hemolysis can be a lifelong asymptomatic condition, it most often presents as anemia when erythrocytosis cannot match the pace of red cell destruction.

Premature destruction of RBCs can occur intravascularly or extravascularly in the reticuloendothelial system, although the latter is more common. Intravascular hemolysis is the destruction of red blood cells in the circulation with the release of cell contents into the plasma. The intravascular mechanisms include direct cellular destruction, fragmentation, and oxidation. Direct cellular destruction is caused by toxins, trauma, or lysis.

The more common extravascular hemolysis is the removal and destruction of red blood cells with membrane alterations by the macrophages of the spleen and liver.

Classification of Hemolytic anemias
1. Red cell abnormality

* Hereditary
* Acquired

2. Extracorpuscular factors

*Immune hemolytic anemias
*Nonimmune hemolytic anemias

Hemolytic anemias can also be classified according to whether the cause of hemolysis is intrinsic or extrinsic to the RBC— damage from within or without.
*Intrinsic causes of hemolysis include abnormalities of hemoglobin, the RBC membrane, or RBC enzymes.
*Extrinsic causes include RBC-directed antibodies, a disordered vasculature, infections, or toxins.

Hemolysis should be considered when a patient experiences acute jaundice or hematuria in the presence of anemia. Symptoms of chronic hemolysis include lymphadenopathy, hepatosplenomegaly, cholestasis, and choledocholithiasis. Other nonspecific symptoms include fatigue, dyspnea, hypotension, and tachycardia.
Hemolytic anemia

Pernicious anemia

Pernicious anemia is a rare blood disorder characterized by inability of the body to properly utilize B12 or cobalamin, which is essential for development of red blood cells. It is a megaloblastic anemia and also known as Addison’s anemia.

Research studies have recently documented that 1.9% of person older than 60 years have undiagnosed pernicious anemia. Approximately 20% of the relatives of patients with pernicious anemia have pernicious anemia.

The three forms of pernicious anemia are congenital pernicious anemia, juvenile pernicious anemia and adult-onset pernicious anemia.

Pernicious anemia results when the body lacks intrinsic factor - a glycoprotein produced by the parietal cells of the stomach lining and that is necessary for absorption of vitamin B12 . Without it, vitamin B12 cannot be properly absorbed in the ileum.

Intrinsic factor deficiency in the adult form of pernicious anemia is caused by atrophic gastritis.

Pernicious anemia also may be associated with autoimmune endocrinopathies and antireceptor autoimmune disease.
Pernicious anemia

Megaloblastic anemia

Megaloblastic anemia, megaloblastosis, refers to a pathogenic process characterized by delay in maturation of the nucleus of blood cell precursors and continuing development of the cytoplasm.

The result of this nuclear-cytoplasmic dissociation is production of cells that are larger than normal due to the defective DNA and RNA synthesis. Megaloblastic changes affect all dividing cells, (e.g. blood, intestine, skin) and the hematopoietic effects involve all blood cell lines.

Megaloblastic anemias can be classified into two major categories based on etiology. The major divisions are vitamin B12 (cobalamin) deficiency and folic acid deficiency. Vitamin B12 and folic acid are both essential for the synthesis of DNA and RNA.

One of the major causes of vitamin B12 deficiency is pernicious anemia, and autoimmune condition that is characterized by the inability of the gastric mucosa to produce intrinsic factor (IF). Intrinsic factor is necessary of the transportation of vitamin B12 across the intestinal mucosa.

In severe megaloblastic anemia, many developing red blood cells are destroyed in the bone marrow before they are released into the circulation.
Megaloblastic anemia