Spherocytose

Spherocytosis, commonly called hereditary spherocytosis, is a group of inherited disorders of the red blood cell membrane characterized by the presence of spherocytes on the blood smear. Most cases result from mutations in genes encoding red cell membrane proteins, including ankyrin-1 (ANK1), spectrin (SPTA1, SPTB), band 3 (SLC4A1), and protein 4.2 (EPB42). The majority of cases are autosomal dominant, with rarer recessive forms.

Pathophysiology involves loss of RBC membrane surface area relative to volume, producing spherical, less deformable cells. Spherocytes are prone to sequestration and destruction in the spleen, leading to chronic extravascular hemolysis. This causes anemia, reticulocytosis, elevated indirect bilirubin, and splenomegaly. Neonatal jaundice and pigmented gallstones are possible. Aplastic crises may occur with parvovirus B19 infection.

Clinical features vary from mild to severe. Common findings include fatigue, pallor, jaundice, and splenomegaly. Some individuals have mild anemia with little symptoms; others require treatment during hemolytic episodes.

Diagnosis typically relies on a combination of findings: a peripheral blood smear showing spherocytes, high mean corpuscular hemoglobin concentration (MCHC), reticulocytosis, and elevated unconjugated bilirubin with a negative Coombs test. Confirmation can involve osmotic fragility testing; modern approaches include eosin-5’-maleimide flow cytometry and ektacytometry.

Management depends on severity. Mild cases may require no treatment beyond folate supplementation. Moderate to severe disease can benefit from splenectomy, which reduces hemolysis but increases infection risk, necessitating appropriate vaccinations and, in children, careful timing. Transfusions may be needed during anemia crises. Genetic counseling is advised for affected families.