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Equine glucose-6-phosphate dehydrogenase deficiency
S L Stockham1, J W Harvey, D A Kinden
1Department of Veterinary Pathology, University of Missouri-Columbia.
Insights
Glucose-6-phosphate dehydrogenase (G6PD) deficiency, an X-linked disorder, was identified in a horse for the first time. This genetic condition caused persistent hemolytic anemia and hyperbilirubinemia in the affected colt.
Area of Science:
- Veterinary Medicine
- Genetics
- Hematology
Background:
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common inherited enzyme disorder in humans, characterized by X-linked inheritance.
- This condition has not been previously documented in equine species.
Observation:
- A case of persistent hemolytic anemia and hyperbilirubinemia in an American Saddlebred colt is described.
- The colt exhibited severe G6PD deficiency with associated erythrocyte abnormalities.
Findings:
- Erythrocytes from the deficient colt showed increased hexokinase and pyruvate kinase activities.
- Decreased reduced glutathione and NADP, along with increased oxidized NADP, were noted.
- Morphological changes included eccentrocytosis, pyknocytosis, anisocytosis, macrocytosis, and increased Howell-Jolly bodies. Electron microscopy revealed unique eccentrocyte structures.
- Heinz body formation in response to acetylphenylhydrazine was more pronounced and smaller in the affected colt's erythrocytes.
Implications:
- This report establishes the first documented case of G6PD deficiency in horses.
- The findings provide insights into the pathophysiology of hemolytic anemia in equines.
- Understanding this condition is crucial for diagnosis and management in affected bloodlines.
Abstract:
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a well-characterized X-linked inherited disorder in humans but has not been reported in horses. We describe a persistent hemolytic anemia and hyperbilirubinemia due to a severe G6PD deficiency in an American Saddlebred colt. Other abnormalities in the colt's erythrocytes as compared with those of healthy horses (n = 22-35) included increased activities of hexokinase and pyruvate kinase, decreased concentrations of reduced glutathione and reduced nicotinamide adenine dinucleotide phosphate (NADP), and increased concentration of oxidized NADP. Morphologic abnormalities included eccentrocytosis, pyknocytosis, anisocytosis, macrocytosis, and increased number of Howell-Jolly bodies. Scanning and transmission electron microscopic examinations revealed that eccentrocytes had contracted to spherical regions and thin collapsed regions. Eccentrocytes were more electron dense than were normal erythrocytes when examined by transmission electron microscopy. When exposed to acetylphenylhydrazine, erythrocytes from the G6PD-deficient colt produced more and smaller Heinz bodies than did erythrocytes from normal horses. Abnormalities in the colt's dam included presence of eccentrocytes and pyknocytes; her average erythrocyte G6PD activity was slightly below the range of reference values.