Acanthocytes should be distinguished from echinocytes, which are also called 'burr cells', which although crenated are dissimilar in that they have multiple, small, projecting spiculations at regular intervals on the cell membrane. Burr cells usually imply uremia, but are seen in many conditions, including mild hemolysis in hypomagnesemia and hypophosphatemia, hemolytic anemia in long-distance runners, and pyruvate kinase deficiency. Burr cells can also arise in vitro due to elevated pH, blood storage, ATP depletion, calcium accumulation, and contact with glass. Acanthocytes should also be distinguished from keratocytes, also called 'horn cells' which have a few very large protuberances.