What is hereditary spherocytosis?
Hereditary spherocytosis (HS) is an inherited disease that causes anemia. If your child has hereditary spherocytosis, either parent may also have the disease. Occasionally, neither parent of an affected child has the disease. In the United States, approximately 1 in 5,000 people have hereditary spherocytosis. The precise incidence in India is unknown.
HS results in the formation of abnormally fragile red blood cells. Red blood cells circulate in the blood and contain hemoglobin, which carries oxygen to all parts of the body, and normal red blood cells are shaped like a disc. However spherocytes are round and fragile and do not change shape to pass through certain organs (e.g. the spleen) as easily as normal red blood cells. Because spherocytes stay in the spleen longer than normal red blood cells, the membrane surrounding the cell becomes damaged, and eventually the red cell is destroyed there.
What are the signs and symptoms of HS?
Symptoms of HS vary, and many patients with HS have a normal hemoglobin level, or only mild anemia. Patients with HS compensate by making more red blood cells, which is measured by the reticulocyte (immature red blood cell) count. However, infection, fever and stress can stimulate the spleen to destroy more red blood cells than usual, causing the hemoglobin level to drop and with jaundice of the skin and whites of the eyes.
Since red blood cells are produced in the bone marrow, sometimes a viral infection (e.g. parvovirus) can cause the bone marrow to stop cell production temporarily causing a drop in hemoglobin with lack of reticulocytes in the blood. This is called an “aplastic crisis” and may last for several days before red blood cell production will resume, during which anemia may be severe enough to require a red blood cell transfusion.
How is HS diagnosed?
The history and physical findings, and the appearance of “spherocytes “in the peripheral blood smear strongly the diagnosis. Confirmatory tests are: