A Heinz body is a cell where hemoglobin is altered, and so they are mutated. It was cause major cell damage and early lysing of the cell. A NADPH deficiency can cause this, along with chronic liver disease, or problems with alpha glob in production. In animals it is associated with dogs, cats, and some primates eating onions. It's also a sign of paracetamol poisoning in cats.

Heinz body