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spherocytosis (microspherocytosis)
sphere-shaped, rather than bi-concave disk shaped, erythrocytes
Etiology:
- immunologically-mediated hemolytic anemias
- hereditary spherocytosis
Pathology:
- molecular defect in one or more of the proteins of the erythrocyte cytoskeleton:
a) spectrin
b) ankyrin
c) Band 3
c) protein 4.2
- the cytoskeletal defect disrupts formation of bi-concave disk shape erythrocytes assume to increase surface area through which oxygen and carbon dioxide can be exchanged
- however; it is thought that spherocytes function adequately to sustain a healthy oxygen supply
- spherocytes are sequestered in the spleen & removed from circulation resulting in hemolyic anemia
Genetics:
- see hereditary spherocytosis
Laboratory:
- complete blood count (CBC)
- elevated MCHC may be a clue to spherocytosis
- MCV is acutally increased
- peripheral blood smear
- spherocytes appears smaller that normal bi-concave disk shaped erythrocytes
- polychromasia
- reticulocyte count may be increased
- direct antiglobulin test (Coombs test)
- positive in immunologically-mediated hemolytic anemias
- negative in hereditary spherocytosis
- erythrocyte osmotic fragility test
- spherocytes have a high osmotic fragility; when placed in hypotonic solutions, spherocytes lyse more easily than normal bi-concave disk shaped erythrocytes
- serum chemistry
- increased serum LDH
- increased serum unconjugated bilirubin (indirect bilirubin)
Management:
- depends upon etiology
- see hereditary spherocytosis
- see spherocyte
- see hemolytic anemia
Related
spherocyte
Specific
hereditary spherocytosis
General
erythrocyte disorder
sign/symptom
References
- Medical Knowledge Self Assessment Program (MKSAP) 11, 16.
American College of Physicians, Philadelphia 1998, 2012
- Wikipedia: Spherocytosis
http://en.wikipedia.org/wiki/Spherocytosis