May 22nd – Keratocytes are erythrocytes with a blister-like vesicle, which may rupture, leaving a “bite-shaped” defect in the cell outline or one or two horn-like projections on the same side of the cell. This process may occur more than once for a given cell, resulting in very irregular shapes. Low numbers of keratocytes may be seen in various situations and may not have any clear clinical significance (e.g. healthy cats may have a few keratocytes in blood). When present in larger numbers or with other poikilocytes, keratocytes can indicate the following: Fragmentation injury: Keratocytes will usually accompany schistocytes and acanthocytes in this setting, Associated conditions include causes of microangiopathic hemolysis (disseminated intravascular coagulation, vasculitis, hemangiosarcoma) and mechanical fragility, e.g. iron deficiency anemia. Oxidant injury: Here keratocytes may accompany eccentrocytes, pyknocytes, and possible Heinz bodies, depending on the oxidant. Liver disease: In cats, keratocytes can be seen in increased numbers in liver disease, e.g. hepatic lipidosis. The mechanism is unclear and could be related to mechanical fragility from alterations in phospholipid or cholesterol composition of the red blood cell membrane (membrane rigidity) or disseminated intravascular coagulation. #365DaysOfMicroscopy