Echinocytes (burr cells)

The RBCs have serrated edges over the entire surface and are uniform in shape. They can be associated with uremia, pyruvate kinase deficiency, hyperlipidemia, liver disease, Vitamin E deficiency and myeloproliferative disorders.
Most artificial causes are excess of EDTA, drying in a humid environment , pH of the medium (including the glass slides).
There is a difference betweeen echinocytes and acantocytes; acantocytes have a few irregularly spicules, not evenly distributed around the RBC membrane.