Hereditary spherocytosis is a genetic blood disorder where red blood cells are shaped like spheres instead of their normal flexible, disc-like shape. It’s the most common inherited cause of hemolytic anemia in people of Northern European descent, affecting roughly 1 in 2,000 people. The condition ranges from so mild you might never notice it to severe enough to require regular blood transfusions.
What Happens to the Red Blood Cells
Normal red blood cells look like flattened discs with a slight indent on each side, almost like a donut that didn’t get its hole punched all the way through. That shape gives them flexibility to squeeze through the tiniest blood vessels in your body. In hereditary spherocytosis, the proteins that hold the cell’s outer membrane to its internal skeleton are deficient or defective. The most commonly affected proteins are spectrin and ankyrin, though others can be involved.
Without that structural support, the membrane becomes unstable. Small pieces of the outer membrane peel away as cells circulate, and the cell gradually loses surface area while keeping the same volume of contents inside. Physics takes over: the cell becomes a rigid sphere. These spherical cells can’t flex and squeeze through the narrow passageways of the spleen the way normal cells can. The spleen traps them, breaks them down, and destroys them far earlier than the typical 120-day lifespan of a healthy red blood cell. That accelerated destruction is what causes the symptoms.
How It’s Inherited
About 75% of cases follow an autosomal dominant pattern, meaning you only need one copy of the mutated gene (from one parent) to develop the condition. If one of your parents has it, you have a 50% chance of inheriting it. The remaining cases are either autosomal recessive, where both parents must carry the gene, or arise from brand-new mutations with no family history at all. In recessive cases, only people who inherit two copies of the defective gene show symptoms.
Symptoms and Severity
The three hallmark signs are anemia (not enough healthy red blood cells), jaundice (a yellowish tint to the skin and eyes), and an enlarged spleen. But these show up to very different degrees depending on the person.
Mild cases, which make up a significant portion of diagnoses, may cause little more than slight fatigue or faint jaundice during times of physical stress or illness. Some people go undiagnosed well into adulthood. In mild disease, the bone marrow compensates by ramping up red blood cell production, with reticulocyte counts (a measure of new red blood cells) typically between 3% and 6%, compared to under 3% in carriers who show no symptoms at all.
Moderate cases involve more noticeable anemia and jaundice, with reticulocyte counts above 6% as the body works harder to replace destroyed cells. Severe cases push reticulocyte counts above 10%, and these patients often need blood transfusions, particularly during childhood. Bilirubin, the yellow pigment released when red blood cells break down, is elevated across all severity levels but climbs higher as the disease worsens.
Complications to Watch For
Aplastic Crisis
The most dangerous acute complication is a transient aplastic crisis, almost always triggered by parvovirus B19 (the virus that causes “fifth disease” in children). This virus temporarily shuts down the bone marrow’s ability to produce new red blood cells. For a healthy person, that brief pause is barely noticeable. For someone with hereditary spherocytosis whose body is constantly churning out replacements for destroyed cells, even a few days without new production can cause hemoglobin to plummet dangerously. This typically requires hospitalization and blood transfusions until the infection passes and the marrow recovers.
Gallstones
All that excess bilirubin from broken-down red blood cells doesn’t just cause jaundice. It also accumulates in the gallbladder and forms pigment gallstones over time. At least 5% of children with hereditary spherocytosis develop gallstones before age 10, and the proportion climbs to 40% to 50% between the teenage years and middle age. Most gallstones form between ages 10 and 30. In one study of 68 children with the condition, the median age at gallstone diagnosis was 11 years.
Hemolytic and Megaloblastic Crises
Hemolytic crises, where red cell destruction spikes suddenly, can be triggered by infections or other stressors. Megaloblastic crises occur when the body runs out of folate, a B vitamin essential for making new red blood cells. Because the bone marrow is working overtime in hereditary spherocytosis, folate demands are higher than normal, making supplementation important.
How It’s Diagnosed
A combination of family history, blood work, and specialized testing usually clinches the diagnosis. On a standard blood count, doctors look for signs like a higher-than-normal concentration of hemoglobin packed into each cell, elevated reticulocyte counts, and raised bilirubin levels. A blood smear under the microscope will often reveal the characteristic spherical cells.
The most reliable confirmatory test is the eosin-5-maleimide (EMA) binding test, a flow cytometry-based test that measures how much of a fluorescent dye binds to a specific protein on the red cell surface. In hereditary spherocytosis, binding is reduced because the membrane has lost material. This test has a sensitivity of 93% and specificity of 98%, meaning it correctly identifies the vast majority of cases and rarely produces false positives. It performs consistently regardless of which specific protein is defective or how severe the disease is.
One critical part of the workup is a direct antiglobulin test (sometimes called a Coombs test), which checks whether the immune system is attacking red blood cells. In hereditary spherocytosis, this test comes back negative. A positive result points toward autoimmune hemolytic anemia instead, a condition that can look very similar on blood work and under the microscope but has a completely different cause and treatment.
Managing the Condition
Folic Acid Supplementation
Because the bone marrow is constantly producing new red blood cells at an accelerated rate, people with hereditary spherocytosis burn through folate faster than average. Daily folic acid supplementation is standard practice, though there’s no universally agreed-upon dose. Prescribed amounts range widely, from 1 mg per day to 5 mg per day depending on the country and the treating physician. The goal is simply to prevent folate deficiency from compounding the anemia.
Blood Transfusions
Children with severe disease may need periodic transfusions, particularly during the first few years of life before other treatments are considered. Aplastic crises triggered by parvovirus also frequently require transfusion support regardless of baseline severity.
Spleen Removal
Since the spleen is where most of the abnormal red blood cells are trapped and destroyed, removing it (splenectomy) dramatically improves anemia in most patients. After surgery, the spherical cells still circulate, but they’re no longer being filtered out and destroyed at such a high rate. Hemoglobin levels typically normalize or near-normalize.
Splenectomy is generally reserved for moderate to severe cases and is usually delayed until at least age 6, and preferably later, because the spleen plays an important role in fighting certain bacterial infections, especially in young children. After the procedure, patients need vaccinations against specific encapsulated bacteria and may take preventive antibiotics, since losing the spleen permanently increases susceptibility to certain serious infections.
For patients who need some intervention but want to preserve partial spleen function, partial splenectomy is sometimes offered. This approach reduces red blood cell destruction while leaving behind enough spleen tissue to maintain some immune protection, though the long-term durability of the benefit is less predictable than with complete removal.
Living With Hereditary Spherocytosis
For people with mild disease, daily life is largely unaffected. You may notice mild jaundice during illnesses or periods of stress, and routine monitoring with blood counts every year or two is typical. Awareness of parvovirus B19 exposure matters, especially for children in school settings where outbreaks of fifth disease are common.
People with moderate or severe disease, particularly those who haven’t had a splenectomy, generally need more frequent monitoring. Periodic ultrasounds to check for gallstones are common starting in childhood. Parents of children with hereditary spherocytosis should know the signs of aplastic crisis: sudden pallor, extreme fatigue, and rapid heart rate, which warrant urgent evaluation. With appropriate monitoring and timely intervention when needed, most people with the condition live normal, full lives.