clinical path 4 (hemolytic anemia)

Heinz bodies

Denatured, precipitated hemoglobin from oxidative injury to the globin; visible as small pale projections on Wright-Giemsa and as dark blue dots on new methylene blue; indicates oxidative hemolytic anemia

RBC agglutination

Grape-like clumps of RBCs held together by antibodies (IgM bridging cells); indicates immune-mediated hemolytic anemia (IMHA); persists after saline dilution, unlike rouleaux

Rouleaux

Stacks of RBCs like a stack of coins caused by decreased negative surface charge (altered zeta potential); not pathologic in horses and cats; in other species suggests increased globulins or fibrinogen (inflammation); disperses with saline, unlike agglutination

Spherocytes

Small, dense, round RBCs with no central pallor; formed when macrophages partially phagocytose antibody/C3b-coated RBCs; indicates IMHA (extravascular hemolysis); best recognized in dogs

Ghost cells

Pale RBC membranes left after hemoglobin escapes through membrane attack complex (MAC) pores; indicates intravascular hemolysis (complement-mediated), seen with IMHA and some infections

Eccentrocytes

RBCs with hemoglobin shifted to one side leaving a clear crescent or “blister” area, from oxidative damage to the RBC membrane; indicates oxidative hemolytic anemia

Chocolate brown mucous membranes

Brown discoloration of blood and mucous membranes from methemoglobin (Fe3+, ferric, oxidized iron that cannot bind oxygen); indicates oxidative injury to the iron of hemoglobin (methemoglobinemia)

Schistocytes

RBC fragments (helmet, triangular, or irregular shapes) from mechanical shearing in fibrin strands or damaged vessels; indicates fragmentation (mechanical) hemolysis such as DIC, hemangiosarcoma, thrombus, or microangiopathy

Acanthocytes

Spur cells with a few irregular, variably sized projections from the RBC surface; indicates fragmentation hemolysis or microangiopathy (e.g., hemangiosarcoma, liver disease); different from echinocytes, which have many short, evenly spaced projections

Keratocytes

“Helmet” or “horn” cells with one or two projections formed when a vacuole or blister ruptures; indicates fragmentation hemolysis (iron deficiency, DIC, hemangiosarcoma, liver disease, chemotherapy)

Species whose RBCs may normally contain <5-10% Heinz bodies

Cats (feline hemoglobin is more susceptible to oxidation, so a small percentage of Heinz bodies can be normal)

Stain used to detect Heinz bodies

New methylene blue (special stain); they are only faintly visible on routine Wright-Giemsa

Typical patient profile for idiopathic (primary, nonassociative) IMHA

Dogs far more than cats; young to middle-aged; predisposed breeds (e.g., Poodles, Cocker Spaniels, Old English Sheepdogs, English Springer Spaniels, Irish Setters)

Common toxicities causing oxidative hemolytic anemia in dogs

Onions, garlic, zinc (pennies minted after 1982), acetaminophen (Tylenol)

Common toxicities causing oxidative hemolytic anemia in cats

Acetaminophen (Tylenol), onions, garlic

Common toxicities causing oxidative hemolytic anemia in ruminants

Brassica plants (kale, rape, and other cruciferous forage), onions, copper

Common toxicities causing oxidative hemolytic anemia in horses

Red maple leaves (wilted or dried), onions

Common RBC infectious agents of cats

Mycoplasma (hemotropic bacteria), Cytauxzoon (protozoa), Babesia (protozoa)

Common RBC infectious agents of cattle

Anaplasma marginale and Anaplasma centrale (bacteria), Babesia (protozoa), Theileria (protozoa)