Echinocytes: Definition, Causes of their Formation, Mechanism, Clinical Significance and Differences with Acanthocytes

The term comes from the Greek word for “sea urchin,” related to its appearance.

Echinocytes are a predominant red blood cell shape abnormality.

Echinocytes are spiculated red blood cells in which the spicules are relatively evenly spaced over their entire surface and are similar in size to sea urchins.

Echinocytes are the predominant red blood cell shape abnormality in human burn patients.

Other names for schistocytes

Echinocytes are also called:

Burr cells

Echinocytes, more commonly known as reversible burr cells, have the peculiarity of presenting sharp spicules, and an artificial change causes schistocytes.

Burr cell means sea urchin cells and is a commonly used synonym.


Berry cells

The term berry cell is less used to refer to schistocytes.


Echinocytes are formed when the surface area of ​​the outer lipid monolayer increases relative to the inner monolayer.

Red blood cells created in this way have changed from a disk shape to spheres covered with short, pointed projections.

Artificial cessation may be due to slow drying of the smear or aging of the blood in the test tube.

Older red blood cells, whether old in circulation or the tube, are more likely to transform from discocyte to echinocyte than younger red blood cells.

The appearance of schistocytes can be related to some diseases, such as uremia and pyruvate kinase deficiency. But these changes can also be artificially caused.

These artificial cells can be confused with actual burr cells or schistocytes.


The presence of burr cells often indicates nothing more than something artificially created and therefore has no diagnostic or clinical significance.

Exposure to excessive concentrations of EDTA (insufficient collection tube)

Artificial red blood cells are most commonly caused by too much EDTA, and this occurs when the sample tube is insufficiently full (dehydrates the red blood cells)

Long-term sample storage before spreading

Another possible echinocyte formation occurs in patients with blood transfusions.

When blood samples are stored at four degrees Celsius, they grow into echinocytes within a few days. But schistocytes manage to transform into red blood cells regularly after they enter a person’s body due to the buffering action of plasma.

Echinocytes may be seen when a blood sample is seen immediately after a transfusion has been performed, but they may later disappear.

The glass effect

Red blood cells can transform into echinocytes when they interact with the glass of a slide during staining of a blood smear for viewing under a microscope.

Some substances released by the slide can raise the pH of the smear, resulting in the formation of schistocytes artificially.

The slide sample should be compared with a wet blood sample to compare whether the appearance of the echinocytes was due to unnatural causes or not.

Slow drying

Echinocytes can also arise from slow-drying in a humid environment.

Other causes

They are usually artificial but can be seen when the individual has other conditions.

Energy depletion

Pyruvate kinase deficiency (note that the cells also resemble acanthocytes, abnormal shapes are prominent only after splenectomy).

Altered hydration

The reduction of the intracellular potassium erythrocyte (K +) causes the dehydration of the red blood cells and the formation of echinocytes.

Altered membrane composition

Drugs that expand the outer leaflet of the red blood cell membrane produce pinocytosis, e.g., salicylates, phenylbutazone, furosemide, and chemotherapeutic agents such as doxorubicin).

Poisoning from snakes such as rattlesnakes, coral snakes, and other snakes can cause echinocytes to form.

Echinocytes can form within 24 hours after a snake bite. This is a useful hematologic marker of this poisoning.

Echinocytes are believed to form from phospholipases in venom, which disrupt phospholipids in the red blood cell membrane.

Unfortunately, because echinocytes are often viewed as an artificial change (usually in stored or “old” blood), they are considered of little pathogenic relevance in most cases.

However, they can provide valuable diagnostic information in the appropriate context, such as in the disease conditions listed above, and should not be ignored.

Possible training mechanism

Echinocytes also form when red blood cells become dehydrated, intracellular pH and calcium rise, and red blood cell ATP is depleted.

Echinocyte spicules are thought to form when the outer portion of the lipid bilayer of red blood cell cells expands outward in contrast to the inner part of the lipid bilayer.

Echinocytic transformation occurs in the presence of fatty acids, lysophospholipids, and amphipathic drugs that are preferentially distributed in the outer half of the lipid bilayer.

Although the mechanisms are unknown, ATP is required to maintain the standard shape and deformability of red blood cells.

Because ATP concentrations must be depleted over several hours to demonstrate changes in shape and deformability in vitro, the concentration does not directly control these properties. Instead, the processes that occur after ATP depletion alter the conditions of cells.

ATP is required for a series of reactions involving the RBC membrane. It is used as a phosphoryl donor in many phosphorylation reactions involving membrane proteins and for the phosphorylation of membrane phosphoinositides.

Provides the energy needed to pump Ca + 2 out of cells. The increase in Ca +2 activates neutral proteases (calpains), which can degrade skeletal membrane proteins, and phospholipase C, which clears phosphoinositides.

ATP is necessary to transport aminophospholipid to the inner half of the lipid bilayer, presumably helping to maintain membrane phospholipid asymmetry.

The relative importance of each of these ATP-dependent reactions for maintaining the shape and deformability of red blood cells has not yet been determined.


Mature echinocytes have 10 to 30 surface projections. These tend to be short, blunt, and relatively evenly distributed around the cell, and there is one distinguishing feature: the cells are centrally pale.

Appearances develop over time, so there is a spectrum of shapes: cells initially resemble normal erythrocytes with subtle projections, becoming increasingly evident in the mature erythrocyte.

Depending on the cause, a late-stage may arise where the cell body becomes dense, and the projections become more pointed.

Meaning of the appearance of echinocytes in the blood

Echinocytes result from an alteration that can be caused by the environment in which the cell is located (red blood cells).

We must consider the pH of the medium, including the glass slides on which the blood smears are prepared, the metabolic state of the blood cell, and the use of chemicals in the preparation.

It should always be remembered that echinocytes can be the product of blood storage or poor preparation of the blood smear (artificial pinocytosis), so the condition of other cells in the sample should be observed. It is determined if the echinocytosis is caused by any pre-existing disease.

Where it is genuine, there will usually be significant systemic disease present. This will most often result from diseases such as uremia, gastrointestinal bleeding, and stomach carcinoma.

Differences Between Echinocytes and Acanthocytes

Echinocytes must be distinguished from acantocytes by two characteristics:

  • The spicules in centrocytes are more variable in shape and size (often blunt or bulbous) and vary in size (height above the membrane and width, particularly along with the projection), unlike schistocytes or globules. On the contrary, created reds have shorter spicules, generally sharp and blunt of uniform length.
  • The spicules are more evenly spaced around their periphery in schistocytes, unlike acantocytes, which are unevenly distributed around the membrane. So, in essence, centrocytes are irregularly spiculated cells, and echinocytes are regularly spiculated cells.
  • Acanthocytes, by contrast, have little or no whiteness in the central area of ​​the cell.