ACANTHOCYTES: CHARACTERISTICS AND RELATED PATHOLOGIES - BIOLOGY - 2024

The acanthocytes are red blood cells with abnormal morphology. They are also known as spiny, spiculated or spur cells. Typically a normal mature red blood cell has a biconcave disc shape that gives it an optimal surface-to-volume ratio for gas exchange and ease of deformation in microcirculation.

This red cell abnormality causes the mature red blood cell to change shape due to abnormalities in cell membrane lipids. The alterations cause the appearance of multiple projections on the membrane attributed to various hemolytic anemias, both inherited and acquired.

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characteristics

In general, they are small cells with sparse spicules, of variable length and width, and irregularly distributed on the surface of the membrane. The proteins that make up the membrane of the acantocytes are normal, while the lipid content is not.

Acanthocyte membrane has more sphingomyelin than normal and less phosphatidylcholine. These changes, reflecting anomalous distributions of phospholipids in plasma, reduce the fluidity of lipids in the erythrocyte membrane, with the consequent change in shape.

In general, neither the nucleated forms of the developing red blood cells nor the reticulocytes have an altered shape. The shape of a typical acantocyte is acquired as the erythrocyte ages.

The mechanism of acanthocyte formation in various pathologies is completely unknown. However, there are several biochemical alterations inherent to the absence of β-lipoproteins such as lipids, phospholipids and serum cholesterol in low concentrations and low concentrations of vitamins A and E in plasma, which can alter the red blood cell.

Pathologies related to the presence of acantocytes

Several diseases have the presence of these abnormal red blood cells, however it is very important to differentiate between some of these anemic pathologies in which the number of acanthoses varies considerably coexisting with normal red blood cells.

The presence of more than 6% of red blood cells with this malformation in a fresh blood smear is a clear indication of a hemolytic pathology.

Congenital abetalipoprotoinemia or Bassen-Kornzweig syndrome

This is a hereditary autosomal recessive syndrome that involves the congenital absence of alloprotein-β from plasma, a protein that is involved in lipid metabolism.

Because of this, plasma lipoproteins containing this apoprotein and plasma triglycerides are also absent and plasma levels of cholesterol and phospholipids are considerably reduced.

In contrast, plasma sphingomyelin is increased due to phosphatidylethanolamine. Acanthocyte abnormality in this syndrome is characterized by the presence of a large amount of sphingolipids in the outer sheet of the cell membrane bilayer, causing an increase in the surface area that causes deformation.

Bassen-Kornzweig syndrome is always accompanied by acantocytosis. Generally the number of acantocytes in the blood is very high. Symptoms of the disease appear after birth, usually with steatorrhea, due to poor fat absorption and developmental delays.

Then at 5 to 10 years retinitis pigmentosa (retinal degeneration) occurs, often leading to blindness. Intentional tremors and ataxia are also manifested, as well as progressive neurological abnormalities that progress to death in the 20s or 30s, where 50% to 100% of the red blood cells are acantocytes.

Hereditary Acanthocytosis

Acanthocytosis in the adult is frequently associated with severe alcoholic hepatocellular disease (alcoholic cirrhosis) or hemolytic anemia with acanthocytes.

In this acquired disorder, erythrocytes show irregular spicules as a result of greatly increased levels of cholesterol in the cell membrane, although phospholipids remain at normal levels.

Due to this, moderate to severe hemolytic anemia may occur depending on the number of circulating acantocytes (> 80%).

On the other hand, acantocytosis with alteration of the cholesterol / erythrocyte lecithin ratio in the red blood cell membrane (hereditary acantocytosis) is a classic companion of Baseen-Kornzweig syndrome.

Neuroacanthocytosis

Acanthocytosis often occurs occasionally in association with a wide range of neurological diseases: among which are muscle atrophy of the Charcot-Marie-Tooth type, chorea-acanthosis, MacLeod syndrome, among others, which are grouped under the name of neuroacantocytosis.

In most of these conditions, it is very rare to find a large number of affected red cells, as in abetalipoprotoinemia (<80% dysmorphic red cells).

Chorea-acantocytosis

Chorea-acantocytosis syndrome, also known as Levine-Critchley syndrome, is a very rare, autosomal recessive disease.

It is characterized by symptoms such as progressive orofacial dyskinesia, neurogenic muscle hypotonia, and muscle degeneration with myotatic hyporeflexia. In affected people, although they do not have anemia, red blood cells are decreased.

In all cases, the neurological manifestations are progressive with the presence of acantocytes in the circulating blood. Acanthocytes do not show alterations in lipid composition and structural proteins.

McLeod syndrome

It is also a chromosomal disease, linked to the X chromosome, in which the neuromuscular, nervous, and hematological system is compromised. Hematologically, it is characterized by the absence of erythrocyte Kx antigen expression, weak expression of Kell antigens, and survival of erythrocytes (acantocytes).

The clinical manifestations are similar to those of Korea, with movement disorders, tics, neuropsychiatric abnormalities such as epileptic seizures.

On the other hand, neuromuscular manifestations include myopathy, sensorimotor neuropathy, and cardiomyopathy. This disease mainly affects men with between 8 and 85% of acantocytes in the blood.

Other disorders with presence of acantocytes

Acanthocytes can be seen in small numbers, in people with malnutrition problems (anemia), with hypothyroidism, after removal of the spleen (splenectomy) and in people with HIV, perhaps due to some nutritional deficiency.

They have also been observed when there is starvation, anorexia nervosa, malabsorption states, in newborn hepatitis after heparin administration and in some cases of hemolytic anemia due to pyruvate kinase deficiency. In all these cases, the β-lipoproteins are normal.

In conditions such as microangiopathic hemolytic anemia, it is common to see deformed red cells of the acantocyte type in circulating blood.

On the other hand, amorphous erythrocytes have also been observed in urinary pathologies, without a specific meaning, such as glomerular hematuria with acantocytes. In this case, there is also a variability in the size of the acantocytes and their count is diagnostic for this disease.

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