Acanthocytes (from the Greek word acantha, which means thorn), or spur cells, are spiculated red cells with a few projections of varying size and surface distribution (see the images below).
The cells appear contracted, dense, and irregular. The morphology of acanthocytes in these various conditions is similar, but the pathogenesis and clinical context often greatly differ. In general, the formation of acanthocytes depends on alteration of the lipid composition and fluidity of the red cell membrane.
Acanthocytosis is a red cell phenotype associated with various underlying conditions. The most frequent and most significant conditions include abetalipoproteinemia (Bassen-Kornzweig syndrome)  and spur cell hemolytic anemia of severe liver disease. Other, less frequent conditions include the following:
- Anorexia nervosa and other malnutrition states
- Infantile pyknocytosis
- McLeod syndrome
- In(Lu) null Lutheran phenotype
- Idiopathic neonatal hepatitis
- Transient hemolysis and stomatocytosis in individuals with alcoholism and mild hemolysis and spherocytosis in individuals with congestive splenomegaly
- Homozygous familial hypobetalipoproteinemia
- Zieve syndrome
- Chronic granulomatous disease (CGD) associated with McLeod red cell phenotype
Acanthocytes should be distinguished from echinocytes (from the Greek word echinos, which means urchin). Echinocytes, or burr cells, appear with multiple small projections that are uniformly distributed on the red cell surface (see the image below).
Echinocytes occur in many conditions, including malnutrition associated with mild hemolysis due to hypomagnesemia and hypophosphatemia, uremia, hemolytic anemia in long-distance runners, and pyruvate kinase deficiency. In vitro, elevated pH, blood storage, ATP depletion, calcium accumulation, and contact with glass can lead to formation of echinocytes.
Who gets Acanthocytosis?
Acanthocytosis, in most of the cases, appear during early infancy or childhood, but it is dependent upon the underlying condition
There is no distinct gender predilection observed
The condition is seen worldwide and can affect any racial or ethnic group
Mutations in the VPS13A gene cause chorea-acanthocytosis. The VPS13A gene provides instructions for producing a protein called chorein; the function of this protein in the body is unknown. Some researchers believe that chorein plays a role in the movement of proteins within cells. Most VPS13A gene mutations lead to the production of an abnormally small, nonfunctional version of chorein. The VPS13A gene is active (expressed) throughout the body; it is unclear why mutations in this gene affect only the brain and red blood cells.
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Other Name for This Condition
What are the Risk Factors for Acanthocytosis?
The risk factors associated with Acanthocytosis include:
A family history of certain disorders that which leads to the formation of acanthocytes
- Severe malnutrition
- Dysfunction of thyroid gland
- Liver diseases and disorders
It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.
Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.
What are the Causes of Acanthocytosis?
Acanthocytosis occurs due to various underlying conditions that may be genetic or acquired. The causative factors of Acanthocytosis may include:
Autosomal recessive abetalipoproteinemia: Mutation in the microsomal triglyceride transfer protein (MTP) on chromosome 4 results in low concentration of cholesterol, VLDL, and LDL in the plasma
Homozygous autosomal dominant familial hypobetalipoproteinemia: It is a milder form of abetalipoproteinemia with APOB mutation on chromosome 2
Neuroacanthocytosis: Mutation in the VPS13A gene on chromosome 21 is observed in this condition. The caudate nucleus, putamen, and pallidum are the parts of the brain affected by atrophy of neurons and gliosis
Idiopathic neonatal hepatitis: This condition manifests as Acanthocytosis and hemolysis, though it resolves spontaneously over several months in 65% of the cases; 20% of the cases end in cirrhosis, 10-20% result in hepatocellular necrosis and death
Infantile pyknocytosis: This is a transient benign condition during early neonatal period. The RBCs are pyknotic (distorted, small, and irregular) and resemble acanthocytes. Even the transfused RBCs become pyknotic suggesting an extrinsic source. The exact cause of this disorder is unknown
Severe malnutrition, eating disorder such as anorexia nervosa, malabsorptive disorder such as celiac disease, and cystic fibrosis (disorder affecting the lungs and other organs): Acanthocytosis may occur due to malabsorption of lipids in the intestine and vitamin E deficiency
Hypothyroidism: 90% of the adults with Acanthocytosis are associated with hypothyroidism
In Acanthocytosis, the concentration of a lipid (called phosphatidylcholine) decreases, cholesterol and sphingomyelin content increases. The cells appear contracted, dense, and irregular. The morphology of the cells is similar during conditions such as abetalipoproteinemia, liver disorders, McLeod syndrome, hypothyroidism, infantile pyknocytosis, neonatal hepatitis, and Zieve syndrome.
What are the Signs and Symptoms of Acanthocytosis?
The signs and symptoms associated with Acanthocytosis are dependent upon the conditions causing Acanthocytosis. These may include:
Hemolytic (blood-related) signs and symptoms:
Ocular (eye) related signs and symptoms:
Loss of night vision, visual acuity, and color vision
Nystagmus (spontaneous horizontal movement of the eyeball) after age 10 years
Ophthalmoplegia (paralysis of eyeball movement) with strabismus (squint)
Gastrointestinal system related signs and symptoms:
- Abdominal distention
- Diarrhea with bulky stools
- Failure to thrive
- Hepatomegaly: enlargement of liver
- Splenomegaly (enlargement of spleen due to increased hemolysis in spleen)
- Ascites (fluid in the peritoneal cavity)
- Neurologic related signs and symptoms:
- Loss of reflexes of the deep tendon
- Loss of sensations primarily occurring in the distal extremities
- Decreased sensation to touch and pain
- Reduced sensitivity to temperature, position
- Decreased muscle strength
Skin related signs and symptoms:
Spider angiomas (dilated central blood vessel with radiating branches on the skin seen in liver dysfunction)
Abdominal wall collateral veins (due to liver dysfunction and portal hypertension)
Recurrent skin infections
Kyphoscoliosis: Abnormal curvature of spine
Pes cavus (high arched foot)
Pes equinovarus (horse foot)
How is Acanthocytosis Diagnosed?
The diagnosis of Acanthocytosis may involve:
Complete evaluation of medical history along with a thorough physical exam
Blood tests, which may indicate the following abnormalities:
- Mild to moderate anemia with elevated reticulocyte count
- Iron and folate deficiency
- Elevated indirect bilirubin, lactate dehydrogenase suggestive of hemolysis
- Elevated liver enzymes and low albumin in liver disorders
- Elevated creatinine kinase in Chorea-Acanthocytosis and McLeod syndrome
- Abnormal lipid profile with cholesterol level less than 50mg/dl, low triglycerides, VLDL, and LDL
- Fat soluble vitamins, such as A, D, E, and K, may show decreased levels
- Prolonged prothrombin time in vitamin K deficiency
- Other tests may also be performed to indicate the following findings:
Elevated fecal fat in abetalipoproteinemia
Hypothyroidism and pan-hypopituitarism (hyposecretion of pituitary hormones)
Nerve conduction velocity (NCV) test: The results may indicate reduced nerve conduction parameters
Intestinal and peripheral nerve biopsy may be necessary when abetalipoproteinemia is suspected
Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.
What are the possible Complications of Acanthocytosis?
Complications associated with Acanthocytosis include:
- Severe anemia due to associated iron and folate malabsorption
- Retinitis pigmentosa leading to night blindness and loss of vision
- Ophthalmoplegia: Paralysis and weakness of the eye muscles
- Neurologic manifestations may be severe with loss of sensations, movement, and ambulation (the affected individuals may be unable to walk)
- McLeod syndrome may cause seizures, heart rhythm abnormalities (arrhythmias), and dilated cardiomyopathy
How is Acanthocytosis Treated?
The treatment of Acanthocytosis is undertaken based upon the underlying causative condition. It may include the following factors:
Medical management of abetalipoproteinemia may include dietary restriction of long-chain fatty acids, with judicious supplementation of medium-chain triglycerides
Replacement of fat soluble vitamins (A, D, E, and K) is essential. Supplementation using vitamin E can help signs and symptoms related to the eye (retina), muscles and nerves
Supplementation of iron and folate
Occupational and physical therapy may be provided to treat disorders that affect movement, ambulation, and sensation (neurological conditions)
Liver disease may be managed through correcting fluid imbalances, metabolic disruptions, and proper nutritional management
Treatment of hypoglycemia
Surgical treatment: A splenectomy (removal of spleen) can help improve hemolysis and is generally performed as a last resort
How can Acanthocytosis be Prevented?
Prevention of Acanthocytosis depends upon preventing and appropriately managing the underlying cause. In some cases, the condition cannot be prevented
Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child (in case of genetic conditions such as abetalipoproteinemia, or neuroacanthocytosis and McLeod syndrome)
Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders.
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