spherocytosis (microspherocytosis)

Introduction

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:
  • spectrin
  • ankyrin
  • Band 3
  • 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

More general terms

• sign/symptom
• erythrocyte disorder

More specific terms

• hereditary spherocytosis

Additional terms

• spherocyte