Hereditary spherocytosis is the most common inherited haemolytic anaemia in northern Europeans, affecting 1 in 5000

It is an autosomal dominant condition. It causes sphere shaped red blood cells that are fragile and easily break down when passing through the spleen.

Pathophysiology

• HS is caused by defects in the red cell membrane, resulting in the cells losing part of the cell membrane as they pass through the spleen, possibly because the lipid bilayer is inadequately supported by the membrane skeleton.
• The best-characterized defect is a deficiency in the structural protein spectrin but quantitative defects in other membrane proteins have been identified, with ankyrin defects being the most common.
• The abnormal red cell membrane in HS is associated functionally with an increased permeability to sodium, and this requires an increased rate of active transport of sodium out of the cells, which is dependent on ATP, produced by glycolysis.
• The surface-to-volume ratio decreases and the cells become spherocytic. Spherocytes are more rigid and less deformable than normal red cells. They are unable to pass through the splenic microcirculation so they have a shortened lifespan.

PC

• jaundice, gallstones, splenomegaly
• some patients go through life asymptomatic
• May develop aplastic, haemolytic, megaloblastic crisis
  • aplastic crisis in the presence of the parvovirus - infects developing erythroblasts and causes temporary abolition of red cell production
  • folate depletion = megaloblastic anaemia
  • chronic haemolysis leads to the formation of pigmented gallstones

Investigations

It is diagnosed by family history and clinical features with spherocytes on the blood film.

• The mean corpuscular haemoglobin concentration (MCHC) is raised on a full blood count.
• Reticulocytes will be raised due to rapid turnover of red blood cells.
• In cases where unsure of diagnosis - the EMA binding test is performed