Stomocytes

Stomocytes, or stomatocytes, are red blood cells that display a characteristic mouth-shaped central pallor, giving the cell a slit-like appearance along its long axis. On a stained peripheral blood smear, the central area of pallor is elongated rather than round, and the cells may appear cup-like in some views.

Stomatocytosis refers to a condition in which a significant fraction of red cells show this stomatocytic morphology. Hereditary stomatocytosis comprises a group of membrane disorders often due to mutations affecting red blood cell permeability and cation homeostasis. Mutations in PIEZO1 and KCNN4 have been associated with hereditary forms, and the condition can include dehydrated (xerocytic) as well as more hydrated variants. Acquired stomatocytosis can be seen in liver disease, alcoholism, certain drug exposures, and other states that alter membrane composition or cell hydration. The clinical significance of stomocytes depends on the underlying disorder and the degree of stomatocytosis, as some cases are mild while others are associated with hemolysis or anemia.

Diagnosis and interpretation rely primarily on the peripheral smear, where the stomocytic morphology is observed. In suspected hereditary cases, genetic testing for related membrane protein genes can confirm the diagnosis, and membrane studies or electrophysiological tests may reveal altered cation flux. Stomocytes are considered in the differential diagnosis of red cell shapes and can be distinguished from other forms such as codocytes or echinocytes by their distinctive slit-like central pallor.