The membrane of red blood cells (RBCs) can undergo a variety of changes leading to morphologic alterations in these cells. When viewed under a freshly prepared peripheral blood smear (PBS), acanthocytes appear as cells with a few spicules of different sizes, projecting from the surface of the RBC membrane at irregular intervals. They result from alterations in membrane lipids and proteins and occur in patients with severe liver dysfunction, neuroacanthocytosis, abetalipoproteinemia, malnutrition, hypothyroidism, post-splenectomy, etc. The clinical significance of acanthocytes lies in their vulnerability to splenic trapping and destruction due to their morphology, which ultimately leads to anemia. When remodeled by the spleen in liver disease patients, acanthocytes develop more blunt spicules and become relatively more spherocytic; these are known as spheroacanthocytes or ‘spur cells.’
It is important to differentiate acanthocytes from echinocytes, which have smaller and more uniform projections and present in patients with end-stage renal disease, liver disease, pyruvate kinase deficiency, etc. The spiculated appearance of RBCs can also result from an ethylene diamine tetra-acetic acid (EDTA) artifact after a delay of more than 6 hours between storage and smear preparation. Therefore for accuracy, it is crucial to ensure that the peripheral blood smear is fresh when read. Spiculated RBCs from EDTA artifact have more uniformly distributed spicules and affect almost all of the RBCs in the film.
Common causes of acanthocytosis are listed here and discussed in detail in the section below:
For maintenance of fluidity of RBC morphology, membrane fluidity is essential. This fluidity is, in turn, controlled by proportions of cholesterol, structural proteins, and phospholipids in the RBC membrane. Diseases such as abetalipoproteinemia, severe liver dysfunction, etc. and neuroacanthocytosis, etc. affect the cholesterol and protein content of the RBC membrane, respectively. Subsequently, the RBC membrane fluidity becomes altered, and the cells undergo morphologic changes leading to the formation of acanthocytes or spur cells. These structural modifications make them susceptible to splenic trapping and destruction, ultimately leading to hemolytic anemia.
Additionally, there has been a different hypothesis suggesting that a component of the RBC membrane skeleton, band 3 is responsible for acanthocyte formation.
Clinical conditions associated with acanthocytosis:
Appropriate intake of calories along with low-fat diet and supplementation of vitamins A, D, E, and K are needed to treat manifestations of the disease. Long-term follow-up to monitor growth and potential complications are needed. Identification of genetic variants in genes such as MTTP may help guide the evaluation of relatives at risk and offer genetic counseling to prospective parents.
Hematologically, acanthocytosis is seen on PBS in these patients. The belief is that genetic mutations lead to the absence of proteins such as XK protein in McLeod syndrome, which leads to acanthocytosis and hemolytic anemia following splenic remodeling. Males with McLeod syndrome are more likely to have acanthocytosis and hemolytic anemia than females. Increased degradation and phosphorylation of membrane proteins along with increased RBC sphingomyelin have implications in the causation of acanthocytosis in chorea-acanthocytosis patients.
Overall, hemolytic anemia associated with acanthocytosis in neuroacanthocytosis syndromes is mild but may, on occasion, warrant blood transfusion. In patients, autologous blood transfusions may be needed to prevent immune-mediated blood transfusion reactions.
Others: Other clinical conditions associated with acanthocytosis are listed below-
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