Hereditary spherocytosis is a genetic blood disorder where red blood cells are shaped like small spheres instead of their normal flexible, disc-like shape. It affects about 1 in 2,000 people of Northern European descent, making it one of the most common inherited anemias in that population. The condition ranges from so mild it goes unnoticed to severe enough to require blood transfusions, but most people fall somewhere in the middle.
Why Red Blood Cells Become Spheres
Normal red blood cells look like flattened discs with a slight indent on each side. That shape gives them flexibility to squeeze through the narrowest blood vessels in your body. The disc shape is maintained by a mesh of proteins just beneath the cell membrane, acting like a skeleton that holds everything in place.
In hereditary spherocytosis, mutations in genes coding for these structural proteins cause parts of the membrane to weaken and break off. As pieces of membrane are lost, the cell can no longer hold its flat shape. It rounds up into a sphere, the way a deflating balloon becomes rounder as it loses surface area. These spherical cells are stiffer, less flexible, and get trapped in the spleen, an organ that normally filters out old or damaged blood cells. The spleen destroys these trapped cells faster than the body can replace them, leading to anemia.
The condition is usually inherited in an autosomal dominant pattern, meaning you only need one copy of the mutated gene (from one parent) to develop it. In roughly 25% of cases, the mutation arises spontaneously with no family history.
How Severity Varies
Doctors classify hereditary spherocytosis into four categories based on how much anemia it causes:
- Mild: Hemoglobin stays between 11 and 15 g/dL, which is close to normal. Many people in this category don’t know they have it until a blood test picks it up incidentally.
- Moderate: Hemoglobin drops to 8 to 11.5 g/dL. This is the most common presentation, and symptoms like fatigue and jaundice are noticeable.
- Moderately severe: Hemoglobin runs between 6 and 8 g/dL. Transfusions may occasionally be needed.
- Severe: Hemoglobin falls below 6 g/dL. These patients are typically transfusion-dependent and often diagnosed in infancy.
Where you fall on this spectrum is largely determined by which membrane protein is affected and how much of it is missing. The severity tends to stay consistent within families, though it’s not perfectly predictable.
Symptoms to Recognize
The three hallmark signs are anemia, jaundice, and an enlarged spleen. Anemia causes fatigue, paleness, shortness of breath with exertion, and a faster heartbeat. Jaundice, a yellowing of the skin and whites of the eyes, happens because the rapid breakdown of red blood cells releases a pigment called bilirubin faster than the liver can process it. An enlarged spleen develops because the organ is working overtime to filter out all those abnormal cells.
In mild cases, the body compensates by producing red blood cells at a faster rate, and you may have few or no symptoms outside of mild jaundice during illness or stress. In children, severe cases can cause slowed growth if not managed. Newborns with hereditary spherocytosis sometimes develop significant jaundice in the first few days of life, occasionally requiring phototherapy or exchange transfusion.
Complications Worth Knowing About
Gallstones are one of the most common complications. The constant breakdown of red blood cells produces excess bilirubin, which accumulates in the gallbladder and forms pigmented stones. This typically shows up between ages 10 and 30, though it can occur earlier. Symptoms include pain in the upper right abdomen, nausea, and sometimes fever. Many patients with moderate or severe disease eventually need their gallbladder removed.
Aplastic crises are rarer but more dangerous. These occur when a viral infection, most often parvovirus B19 (the virus that causes “fifth disease” in children), temporarily shuts down the bone marrow’s ability to produce new red blood cells. For someone whose body is already destroying cells at an accelerated rate, even a brief pause in production can cause hemoglobin to plummet dangerously. Aplastic crises can lead to acute heart failure and typically require hospitalization and transfusion support. The good news is that once you’ve had a parvovirus B19 infection, you’re immune for life, so this type of crisis usually happens only once.
How It’s Diagnosed
A standard blood test often provides the first clue: spherical red blood cells visible on a blood smear, combined with signs of increased red blood cell destruction (elevated bilirubin, elevated reticulocyte count). But confirming the diagnosis requires more targeted testing.
The most accurate screening test available uses a fluorescent dye called eosin-5-maleimide (EMA) that binds to red blood cell membrane proteins. In hereditary spherocytosis, those proteins are reduced, so the cells glow less brightly. This test has a sensitivity of 93% and a specificity of 98%, meaning it catches nearly all true cases while rarely producing false positives.
The older standard test, the osmotic fragility test, is less reliable. It measures how easily red blood cells burst when placed in diluted salt water. Spherocytes swell and pop more readily than normal cells. But this test catches only 68% of cases when run on fresh blood and 81% on incubated samples, missing a significant number of milder cases. If your doctor suspects hereditary spherocytosis and an osmotic fragility test comes back normal, it’s worth asking about the EMA binding test.
Living With Hereditary Spherocytosis
For mild cases, management is straightforward. Your body needs extra folic acid to keep up with the increased pace of red blood cell production. Folic acid supplementation is standard, typically 1 mg daily for anyone over age one. Regular monitoring with blood tests helps catch any changes in severity, particularly during illness or pregnancy when the body is under extra stress.
Moderate cases require closer follow-up and may need occasional blood transfusions during hemolytic or aplastic crises. Routine vaccinations are important, especially against parvovirus-related complications.
When Spleen Removal Is Considered
Since the spleen is where most of the red blood cell destruction happens, removing it dramatically improves anemia in hereditary spherocytosis. The red blood cells are still spherical afterward, but without the spleen filtering them out, they survive much longer in circulation. Total splenectomy raises hemoglobin by an average of 3.6 g/dL, which is enough to move most patients from moderate anemia into a near-normal range.
Splenectomy is generally not recommended for mild cases and is reserved for those with moderate to severe disease. Because the spleen plays a critical role in fighting certain bacterial infections, especially in young children, the procedure is typically delayed until at least age 6 and is not performed before age 5 except in unusual circumstances. Before surgery, patients receive vaccinations against specific bacteria (pneumococcus, meningococcus, and Haemophilus influenzae) and will take a daily preventive antibiotic afterward, often for years.
For young children with severe anemia who can’t wait until age 6, partial splenectomy offers a compromise. This procedure removes 80 to 90% of the spleen while leaving enough tissue intact to maintain some immune protection. It raises hemoglobin by about 2.2 g/dL and reduces the rate of red blood cell destruction, with results that remain stable for at least six years in most cases. The tradeoff is that the spleen remnant can regrow over time, and some patients eventually need a total splenectomy later if hemoglobin levels fall again or the regrowing spleen causes discomfort.
A meta-analysis comparing the two approaches in children found that total splenectomy is more effective at correcting anemia and reducing reticulocyte counts, but partial splenectomy provides meaningful, lasting improvement while preserving immune function during the years when infection risk is highest.