Changes

'''Heinz bodies''' are inclusion bodies that form within erythrocytes as a result of '''oxidative injury''' to the cell. Named after Robert Heinz, the German physician who first described them, they consist of precipitated haemoglobin and their presence can result in premature phagocytosis of erythrocytes <ref name="Schalm"> Weiss, D and Wardrop, K (eds) (2010) '''Schalm's Veterinary Haematology, Sixth edition''' Wiley-Blackwell p. 134</ref>  

'''Heinz bodies''' are inclusion bodies that form within erythrocytes as a result of '''oxidative injury''' to the cell. Named after Robert Heinz, the German physician who first described them, they consist of precipitated haemoglobin and their presence can result in premature phagocytosis of erythrocytes <ref name="Schalm"> Weiss, D and Wardrop, K (eds) (2010) '''Schalm's Veterinary Haematology, Sixth edition''' Wiley-Blackwell p. 134</ref>  

Oxidative toxins damage the sulphydryl groups of the globin chains of haemoglobin resulting in the formation of Heinz bodies (HBs). These are seen as unstained projections on the cell membrane with Romanowsky stain, but stain with new methylene blue. Oxidative injury may also result in eccentrocyte formation +/- methaemoglobinaemia. Many substances can cause oxidative damage. Affected cells may be phagocytosed in the spleen or, if severely damaged, may undergo haemolysis within the circulation - there may be both extravascular and intravascular haemolysis. This type of anaemia is regenerative. References: [[/en.wikivet.net/NationWide Laboratories|NationWide Laboratories]]  

Oxidative toxins damage the sulphydryl groups of the globin chains of haemoglobin resulting in the formation of Heinz bodies (HBs). These are seen as unstained projections on the cell membrane with Romanowsky stain, but stain with new methylene blue. Oxidative injury may also result in eccentrocyte formation +/- methaemoglobinaemia (see below). Many substances can cause oxidative damage. Affected cells may be phagocytosed in the spleen or, if severely damaged, may undergo haemolysis within the circulation - there may be both extravascular and intravascular haemolysis. This type of anaemia is regenerative. References: [[NationWide Laboratories]]  

===Structure of haemoglobin===

===Structure of haemoglobin===

* '''Methaemoglobinaemia''' formation occurs when the '''iron in the haemoglobin molecule''' is oxidised to the ferric (3+) state. In normal circumstances the methaemoglobin reductase enzyme reduces ferric (3+) back to ferrous (2+) but this system can become overwhelmed in some circumstances.<ref name="CVT"></ref> This is the only form of oxidative damage which is reversible.

* '''Methaemoglobinaemia''' formation occurs when the '''iron in the haemoglobin molecule''' is oxidised to the ferric (3+) state. In normal circumstances the methaemoglobin reductase enzyme reduces ferric (3+) back to ferrous (2+) but this system can become overwhelmed in some circumstances.<ref name="CVT"></ref> This is the only form of oxidative damage which is reversible. Methaemoglobin is a brownish compound formed by the oxidation of iron in haemoglobin from the ferrous to the ferric state. When present in quantity it leads to a muddy cyanotic discolouration of mucous membranes. Usually it accounts for less than 1.1% of haemoglobin. It is increased due to oxidative damage caused by toxins which may also cause Heinz body and eccentrocyte formation. Methaemoglobinaemia results from either increased production due to oxidative injury or decreased reduction of methaemoglobin to Hb. Congenital methaemoglobinaemia has been reported due to deficiency of the RBC enzyme NADH-methaemoglobin reductase. References: [[/en.wikivet.net/NationWide Laboratories|NationWide Laboratories]]