Equine glucose-6-phosphate dehydrogenase deficiency.

The research article presents a case of Glucose-6-phosphate dehydrogenase (G6PD) deficiency in an American Saddlebred colt, a condition that is widely studied in humans but not previously reported in horses, exhibiting persistent hemolytic anemia and hyperbilirubinemia accompanied by other erythrocyte abnormalities.

Introduction to G6PD Deficiency

• Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a well-documented, genetically inherited disorder in humans.
• The disorder affects the function of red blood cells causing anemia, a condition characterized by a lack of healthy red blood cells in the body, and hyperbilirubinemia, which is an excessive level of bilirubin, a waste material in the bloodstream
• In this research, a case of severe G6PD deficiency is reported in an American Saddlebred colt, a type of horse breed.

Erythrocyte Abnormalities in the Colt

• Various abnormal conditions were discovered in the colt’s red blood cells in comparison to healthy horses, such as increased activity of hexokinase and pyruvate kinase, decreased levels of reduced glutathione and NADP, and increased amounts of oxidized NADP.
• Morphological conditions including eccentrocytosis (a condition characterized by off-center, hemoglobin concentration within red blood cells), pyknocytosis (the presence of abnormally small and distorted red blood cells), anisocytosis (red blood cells of unequal sizes), macrocytosis (red blood cells larger than normal), and an increased number of Howell-Jolly bodies (residual fragments of DNA in circulating red blood cells) were also observed.

Microscopic Examination and Tests

• Scanning and transmission electron microscope examinations showed that the eccentrocytes had contracted to create spherical regions and thin, collapsed sections, and they appeared denser than normal red blood cells.
• The colt’s red blood cells, when exposed to acetylphenylhydrazine, produced more and smaller Heinz bodies (precipitated hemoglobin within red blood cells, usually due to oxidative stress) than normal horses.

Findings in the Colt’s Dam (Mother)

• Abnormalities were also noted in the colt’s dam, including the presence of eccentrocytes and pyknocytes – abnormally shrunk and irregularly shaped red blood cells.
• Her average red blood cell G6PD activity was somewhat below the reference range, suggesting a possible genetic link.