Selected red cell shapes

Eight shape findings on a stained peripheral blood smear

Red blood cell (RBC) shape is assessed where cells lie singly or just touch and normal central pallor remains visible. Thick areas distort shape and obscure pallor. Normal pallor occupies about one third of a cell's diameter.¹

May-Grünwald Giemsa-stained human blood smears. Letters and arrows identify source panels; crops are not at a common scale. Source patients had coronavirus disease 2019 (COVID-19); these shapes are nonspecific.²

Echinocyte A

Short, evenly spaced projections. Often artifact; also uremia. Acanthocytes have irregular projections.

Acanthocyte B

Uneven projections of varied length. Severe liver disease; lipid disorders. Compare with regular echinocytes.

Spherocyte D

Dense, no central pallor (single arrow). Immune hemolysis; hereditary spherocytosis. Thick areas hide normal pallor.

Elliptocyte D

Elongated ovals (paired arrows). Hereditary elliptocytosis; iron deficiency. Large ovals suggest megaloblastic change.

Target cell E

Stained center, pale ring, outer rim. Thalassemia; liver disease; hemoglobin variants. Uneven distribution suggests artifact.

Stomatocyte F

Slit-like central pallor. Hereditary stomatocytosis; liver disease. Slow drying can mimic this.

Teardrop cell G

One tapered end; a dacrocyte. Marrow fibrosis/infiltration; megaloblastic anemia. Artifact tails often point the same way.

Schistocyte H

Angular or helmet-shaped fragment. Microangiopathic or mechanical damage. Follow counting and urgent-review policy.

Schistocytes are red cell fragments. Their significance depends on the number present and the other smear findings; follow the laboratory's counting and urgent-review criteria.³