Inherited haemolytic anaemia
An autosomal dominant condition in which the red cells are spherical. Hereditary elliptocytosis is an autosomal dominant condition similar but clinically milder than hereditary spherocytosis.
Commonest inherited haemolytic anaemia; 1 in 5000.
There is a high new mutation rate with 25% of patients not having an affected parent. The underlying cause is a weakness in the link between the cytoskeleton and the red cell membrane. This may be a quantitative or functional abnormality of any of the membrane proteins (spectrin, ankyrin, protein 4.1). Part of the abnormally weak cell membrane is removed as the cells pass through the spleen, changing the cell shape from a biconcave disc to a sphere. These cells are more rigid than normal and are subject to further damage in the microcirculation.
Spherocytosis may present as neonatal jaundice or anaemia with chronic malaise and splenomegaly. Normal infections cause a relative increase in haemolysis and may result in jaundice. Complications as for haemolytic anaemia may occur.
Anaemia is usually mild. A blood film will demonstrate the spherocytes, but this cell morphology is not diagnostic. The diagnosis can be confirmed by demonstrating the osmotic fragility of the red blood cells.
Splenectomy is often required but should be delayed to adulthood if possible to prevent overwhelming septicaemia from encapsulated organisms. Patients are given pneumococcal vaccinations and prophylactic antibiotics post splenectomy.