Spherocytosis
Encyclopedia
Spherocytosis is an auto-hemolytic
anemia
(a disease of the blood) characterized by the production of red blood cell
s (RBCs), or erythrocytes, that are sphere-shaped, rather than bi-concave disk shaped. Spherocytes are found in hereditary spherocytosis
and autoimmune hemolytic anemia
.
It almost always refers to hereditary spherocytosis
. This is caused by a molecular defect in one or more of the proteins of the red blood cell cytoskeleton
, including, spectrin
, ankyrin
, Band 3, or Protein 4.2. Because the cell skeleton has a defect, the blood cell contracts to its most surface-tension efficient and least flexible configuration, a sphere. The sphere-shaped red blood cells are known as spherocytes. Though the spherocytes have a smaller surface area through which oxygen
and carbon dioxide
can be exchanged, they in themselves perform adequately to maintain healthy oxygen supplies. However, they have a high osmotic
fragility--when placed into water, they are more likely to burst than normal red blood cells. These cells are more prone to physical degradation.
They are most commonly found in immunologically-mediated hemolytic anemia
s and in hereditary spherocytosis
, but the former would have a positive direct Coombs test and the latter would not. The misshapen but otherwise healthy red blood cells are mistaken by the spleen
for old or damaged red blood cells and it thus constantly breaks them down, causing a cycle whereby the body destroys its own blood supply (auto-hemolysis
).
The term "non hereditary spherocytosis" is occasionally used, albeit rarely.
Hemolysis
Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
(a disease of the blood) characterized by the production of red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...
s (RBCs), or erythrocytes, that are sphere-shaped, rather than bi-concave disk shaped. Spherocytes are found in hereditary spherocytosis
Hereditary spherocytosis
Hereditary spherocytosis is a genetically-transmitted form of spherocytosis, an auto-hemolytic anemia characterized by the production of red blood cells that are sphere-shaped rather than bi-concave disk shaped , and therefore more prone to hemolysis.-Symptoms:As in non-hereditary spherocytosis,...
and autoimmune hemolytic anemia
Autoimmune hemolytic anemia
Autoimmune hemolytic anemia occurs when antibodies directed against the person's own red blood cells cause the RBCs to burst , leading to insufficient plasma concentration. The lifetime of the RBCs is reduced from the normal 100–120 days to just a few days in serious cases...
.
It almost always refers to hereditary spherocytosis
Hereditary spherocytosis
Hereditary spherocytosis is a genetically-transmitted form of spherocytosis, an auto-hemolytic anemia characterized by the production of red blood cells that are sphere-shaped rather than bi-concave disk shaped , and therefore more prone to hemolysis.-Symptoms:As in non-hereditary spherocytosis,...
. This is caused by a molecular defect in one or more of the proteins of the red blood cell cytoskeleton
Cytoskeleton
The cytoskeleton is a cellular "scaffolding" or "skeleton" contained within a cell's cytoplasm and is made out of protein. The cytoskeleton is present in all cells; it was once thought to be unique to eukaryotes, but recent research has identified the prokaryotic cytoskeleton...
, including, spectrin
Spectrin
Spectrin is a cytoskeletal protein that lines the intracellular side of the plasma membrane of many cell types in pentagonal or hexagonal arrangements, forming a scaffolding and playing an important role in maintenance of plasma membrane integrity and cytoskeletal structure...
, ankyrin
Ankyrin
Ankyrins are a family of adaptor proteins that mediate the attachment of integral membrane proteins to the spectrin-actin based membrane skeleton. Ankyrins have binding sites for the beta subunit of spectrin and at least 12 families of integral membrane proteins...
, Band 3, or Protein 4.2. Because the cell skeleton has a defect, the blood cell contracts to its most surface-tension efficient and least flexible configuration, a sphere. The sphere-shaped red blood cells are known as spherocytes. Though the spherocytes have a smaller surface area through which oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
and carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
can be exchanged, they in themselves perform adequately to maintain healthy oxygen supplies. However, they have a high osmotic
Osmosis
Osmosis is the movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides...
fragility--when placed into water, they are more likely to burst than normal red blood cells. These cells are more prone to physical degradation.
They are most commonly found in immunologically-mediated hemolytic anemia
Hemolytic anemia
Hemolytic anemia is a form of anemia due to hemolysis, the abnormal breakdown of red blood cells , either in the blood vessels or elsewhere in the human body . It has numerous possible causes, ranging from relatively harmless to life-threatening...
s and in hereditary spherocytosis
Hereditary spherocytosis
Hereditary spherocytosis is a genetically-transmitted form of spherocytosis, an auto-hemolytic anemia characterized by the production of red blood cells that are sphere-shaped rather than bi-concave disk shaped , and therefore more prone to hemolysis.-Symptoms:As in non-hereditary spherocytosis,...
, but the former would have a positive direct Coombs test and the latter would not. The misshapen but otherwise healthy red blood cells are mistaken by the spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
for old or damaged red blood cells and it thus constantly breaks them down, causing a cycle whereby the body destroys its own blood supply (auto-hemolysis
Hemolysis
Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
).
The term "non hereditary spherocytosis" is occasionally used, albeit rarely.
See also
- AnemiaAnemiaAnemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
- BloodBloodBlood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
- Blood diseases
- Red blood cells
- Hereditary diseases