Hereditary spherocytosis
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Hereditary spherocytosis is a genetic disorder of the red blood cells that makes them prone to hemolysis.
Signs and symptoms
Hemolysis under stress conditions, or even spontaneously, is the main feature.
Diagnosis
Spherocytes (globular rather than discocyte or cushion-shaped) erythrocytes on the blood smear are diagnostic of spherocytosis.
There are several non-hereditary causes for spherocytosis, mainly autoimmune hemolytic anemia.
Pathophysiology
Erythrocytes become spherocytes when the connections between the cytoskeleton and the cell membrane are disrupted. These connections are maintained by an intricate network of proteins, and if one of these proteins is missing, the red cell cannot maintain its discocyte form and becomes globular.
Not all proteins deficits lead to spherocytosis: normally ankyrin/spectrin deficits are the most common deficits in spherocytosis, followed by Band 3 deficits and in Japanese populations protein 4.2 deficits are common.
Other protein deficits can cause Hereditary Elliptocytosis, Pyropoikilocytosis or Stomatocytosis.