ABSTRACT
Diseases or abnormalities of the haemolymphatic system are often encountered in equine medicine. Evaluation of the blood-forming organs and lymphatic tissues can provide information as diverse as bone marrow integrity, cellular response to infection, haemostasis competency and immune system status. Haemolysis can occur extravascularly or intravascularly. Extravascular haemolysis results in increased unconjugated bilirubin and, eventually, conjugated bilirubin, resulting in clinical icterus. Intravascular haemolysis as a primary mechanism causes haemoglobinaemia and haemoglobinuria. Diagnosis is based on suggestive clinical signs and laboratory evidence of haemolysis, including potentially severe anaemia that increasingly becomes macrocytic, hypochromic with anisocytosis and an increasing red cell distribution width. Intravascular haemolysis for any reason warrants a guarded to poor prognosis. If the disease is detected early and the dose of toxin was minimal, the animal may recover. Although red maple leaf toxicosis is the most common cause of Heinz body haemolytic anaemia in horses, other oxidant compounds also have the capacity to denature haemoglobin.
