ConditionBlood & immune system
Stomatocytosis
Stomatocytosis is a group of red blood cell disorders in which the cell membrane leaks sodium and potassium, so cells swell or shrink with water. Under the microscope, many red cells show a mouth-like slit (stoma) instead of a round pale center. Inherited forms cause hemolytic anemia of varying severity, jaundice, gallstones and, often, iron overload. Unlike in some similar conditions, removing the spleen is usually avoided because it greatly increases the risk of dangerous blood clots.
Also called: Hereditary stomatocytosis, hereditary xerocytosis (dehydrated stomatocytosis), overhydrated hereditary stomatocytosis, stomatocytic anemia
At a glance
- What it is
- Red cell membrane disorders with abnormal salt and water handling, causing stomatocytes and hemolysis.
- Main inherited types
- Dehydrated hereditary stomatocytosis (xerocytosis, most common, often PIEZO1), overhydrated hereditary stomatocytosis, and rarer variants.
- Inheritance
- Usually autosomal dominant.
- Symptoms
- Mild to moderate anemia, tiredness, jaundice, gallstones, enlarged spleen; some people have none.
- Key risks
- Iron overload, even without transfusions; blood clots, especially after splenectomy.
- Treatment
- Folic acid, monitoring, transfusions when needed, iron chelation; splenectomy generally avoided.
When to get help
Call 911 or go to the ER
- Sudden breathlessness, chest pain, or a swollen, painful leg, especially after splenectomy (possible blood clot): call 911 or your local emergency number
- Severe paleness, fainting or a racing heart
See a doctor within a day or two
- Worsening jaundice, dark urine and tiredness, especially with an infection
- Pain in the upper right abdomen with fever or yellowing (possible gallstone complication)
- Severe anemia in pregnancy
Book a routine appointment
- Unexplained mild anemia with jaundice or a family history of anemia or gallstones at a young age
- A high potassium result on a blood test that does not match how you feel (possible pseudohyperkalemia)
- High ferritin or iron levels in someone with a known red cell membrane disorder
What happens in stomatocytosis
Red cells must stay flexible to squeeze through tiny vessels. Their size and shape depend on precise control of sodium, potassium and water by membrane channels. In stomatocytosis, gene changes make the membrane leaky:
- Overhydrated cells take on too much sodium and water, becoming swollen and fragile.
- Dehydrated cells (xerocytosis) lose potassium and water, becoming dense and rigid.
Either way, the spleen removes abnormal cells early, causing hemolytic anemia.
Types
| Type | Gene(s) | Features |
|---|---|---|
| Dehydrated hereditary stomatocytosis (hereditary xerocytosis) | PIEZO1, sometimes KCNN4 | Most common; mild to moderate anemia, often well compensated; iron overload common; sometimes fluid around the baby before birth |
| Overhydrated hereditary stomatocytosis | RHAG | Rare; more severe hemolysis; many stomatocytes on the smear |
| Familial pseudohyperkalemia | ABCB6 and others | Potassium leaks out of cells in stored blood samples, giving falsely high results; usually no anemia |
| Cryohydrocytosis and related forms | SLC4A1 and others | Cells leak more at cold temperatures |
Acquired stomatocytes
Stomatocytes can also appear on blood smears with heavy alcohol use, liver disease, some medicines, and as a preparation artifact. These are not hereditary stomatocytosis.
Symptoms
- tiredness and weakness from anemia
- pale skin
- yellowing of the skin or eyes (jaundice)
- dark urine during episodes of increased hemolysis
- gallstones, sometimes at a young age
- enlarged spleen
- symptoms of iron overload in some adults
Some people have no symptoms and are diagnosed after unusual blood test results.
Diagnosis
- Complete blood count: anemia or compensated hemolysis; red cell indices may be unusual (for example, high MCHC in xerocytosis).
- Blood smear: stomatocytes, sometimes target cells.
- Hemolysis tests: high reticulocytes and bilirubin, low haptoglobin.
- Osmotic gradient ektacytometry: a specialized test of red cell deformability that distinguishes membrane disorders.
- Genetic testing: confirms the type, such as PIEZO1 variants.
- Ferritin and iron studies.
Stomatocytosis is often initially misdiagnosed as hereditary spherocytosis. Getting the diagnosis right is crucial, because treatment differs.
Treatment
- Folic acid supplements to support red cell production.
- Regular monitoring of blood counts and bilirubin.
- Blood transfusions for severe anemia, pregnancy or crises.
- Iron monitoring and chelation: iron overload can develop even without transfusions, so ferritin and sometimes liver MRI are checked; chelation or, if no anemia limits it, phlebotomy may be used. See iron overload.
- Gallbladder removal for symptomatic gallstones.
- Avoid splenectomy: in stomatocytosis, removing the spleen offers little benefit and is associated with a high risk of serious blood clots, including in the lungs, portal vein and pulmonary hypertension. It is generally not recommended.
Outlook
Most people with hereditary stomatocytosis have mild to moderate disease and a normal lifespan with monitoring. The main long-term issues are iron overload, gallstones and clot risk, all of which can be managed. Genetic counseling helps families understand inheritance.
Frequently asked questions
What is stomatocytosis?
Stomatocytosis is a group of red blood cell disorders in which the cell membrane leaks sodium and potassium, upsetting water balance. Affected cells look like they have a mouth-like slit under the microscope and are destroyed early, causing hemolytic anemia.
What causes hereditary stomatocytosis?
It is caused by inherited changes in genes that control ion channels in the red cell membrane, most often PIEZO1 in dehydrated stomatocytosis (xerocytosis) and RHAG in the overhydrated form. Most forms are passed on in an autosomal dominant pattern.
Why is splenectomy avoided in stomatocytosis?
Removing the spleen in stomatocytosis often does not improve anemia much and is linked to a high risk of serious blood clots, including clots in the lungs and veins of the abdomen and pulmonary hypertension. For this reason, doctors generally advise against it.
Is stomatocytosis the same as spherocytosis?
No. Both are inherited red cell membrane disorders causing hemolytic anemia, but they involve different genes and cell shapes. Spherocytosis often improves after splenectomy, while splenectomy is generally avoided in stomatocytosis because of clot risk. Specialized tests tell them apart.
Sources
This guide was written from current patient and clinical guidance, including:
- MedlinePlus Genetics: Hereditary xerocytosis; Overhydrated hereditary stomatocytosis
- National Organization for Rare Disorders (NORD): Hereditary stomatocytosis
- British Society for Haematology: Guideline for the laboratory diagnosis of red cell membrane disorders
- American Society of Hematology: Hemolytic anemia
- Genetic and Rare Diseases Information Center (GARD): Dehydrated hereditary stomatocytosis