Hereditary Spherocytosis

Hereditary spherocytosis is an inherited disorder of the red-cell membrane in which defects in cytoskeletal proteins reduce the cell's surface-to-volume ratio, producing spherical, fragile red cells (spherocytes). These cells are trapped and destroyed in the spleen, causing chronic hemolytic anemia. It is one of the most common inherited hemolytic anemias of red-cell membrane origin in populations of northern European ancestry.

Definition

Hereditary spherocytosis is an inherited hemolytic anemia caused by defects in red-cell membrane or cytoskeletal proteins (such as spectrin, ankyrin, band 3, or protein 4.2) that reduce membrane surface area, producing spherocytes that are prematurely destroyed in the spleen.

Scope

This topic covers the membrane-protein basis of the disorder, how loss of membrane surface produces spherocytes, the role of splenic destruction in hemolysis, and the inheritance pattern. Grouped here among inherited red-cell disorders, it is a membrane defect rather than a disorder of hemoglobin itself. This is a reference entry and does not provide individualized clinical guidance.

Core questions

• How do defects in membrane and cytoskeletal proteins generate spherical red cells?
• Why does loss of membrane surface area lead to splenic trapping and hemolysis?
• How do the genetics and the modifying effect of the spleen account for the clinical spectrum?

Key concepts

• Red-cell membrane skeleton (spectrin, ankyrin, band 3, protein 4.2)
• Loss of membrane surface-to-volume ratio
• Spherocyte formation
• Splenic sequestration and extravascular hemolysis
• Osmotic fragility
• Autosomal inheritance (commonly dominant)
• Reticulocytosis and compensated hemolysis

Mechanisms

The red-cell membrane is supported by a protein skeleton anchored to the lipid bilayer through vertical interactions among spectrin, ankyrin, band 3, and protein 4.2. In hereditary spherocytosis, inherited defects in one of these proteins weaken the link between the skeleton and the bilayer, so the cell sheds portions of its membrane. Losing surface area while retaining volume converts the normal biconcave disc into a sphere—the least surface for a given volume—and a sphere is poorly deformable. As these rigid spherocytes traverse the narrow channels of the splenic cords, they are retained, further conditioned, and ultimately engulfed by macrophages (extravascular hemolysis). The marrow compensates with increased red-cell production, so the clinical picture ranges from compensated hemolysis to overt anemia depending on the severity of the membrane defect and the activity of the spleen.

Clinical relevance

Hereditary spherocytosis is a leading inherited cause of membrane-related hemolytic anemia and a common consideration when spherocytes and reticulocytosis are seen together. Understanding the membrane mechanism explains both the laboratory findings and the central role of the spleen. This entry is for reference and education and is not a basis for individual diagnosis or treatment.

Epidemiology

Hereditary spherocytosis is among the most common inherited hemolytic anemias in people of northern European ancestry, with most cases following an autosomal dominant pattern and a minority arising from recessive inheritance or new mutations. Bolton-Maggs and colleagues summarize its diagnostic and clinical features in a haematology guideline; unlike the hemoglobin disorders, its distribution is not linked to malaria selection.

History

The condition was described clinically in the late nineteenth and early twentieth centuries—its eponym Minkowski-Chauffard syndrome recalls early descriptions—and the central role of the spleen was recognized when splenectomy was found to relieve the anemia. Twentieth-century work on the red-cell membrane skeleton, associated with investigators such as Mohandas and Gallagher, identified the cytoskeletal protein defects that reduce membrane surface area and produce spherocytes, placing the disorder on a molecular footing.

Key figures

• Narla Mohandas
• Patrick G. Gallagher
• Silverio Perrotta
• Oskar Minkowski
• Anatole Chauffard

Seminal works

• perrotta-2008
• bolton-maggs-2011

Frequently asked questions

Is hereditary spherocytosis a hemoglobin disorder?

No. It is a defect of the red-cell membrane skeleton rather than of hemoglobin. It is grouped with the inherited red-cell disorders because it causes an inherited hemolytic anemia, but its mechanism is loss of membrane surface area rather than abnormal hemoglobin.

Why does the spleen matter so much in hereditary spherocytosis?

Spherocytes are rigid and poorly deformable, so they are selectively trapped and destroyed in the narrow passages of the spleen. The spleen is therefore the principal site of red-cell destruction in this disorder.