• Open Access

Persistent Hyperammonemia in Two Related Morgan Weanlings

Authors

  • Rebecca S. McConnico DVM,

    1. Department of Food Animal and Equine Medicine, North Carolina State University, College of Veterinary Medicine, Raleigh, NC
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    • 2

      Boren Veterinary Teaching Hospital, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078

  • Wendy M. Duckett,

    1. Department of Food Animal and Equine Medicine, North Carolina State University, College of Veterinary Medicine, Raleigh, NC
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  • Philip A. Wood

    1. Department of Comparative Medicine, Schools of Medicine and Dentistry, University of Alabama at Birmingham, AL
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Abstract

Persistent hyperammonemia was diagnosed in 2 Morgan fillies with clinical signs that developed early in the post-weaning period. Diagnostic evaluation, including routine serum chemistries, CBC, liver biopsy, hepatic ultrasonography, liver function test, and necropsy findings did not support a toxic, developmental, or infectious cause. Abnormal serum amino acid and urine orotic acid concentrations suggest that the foals may have had an inherited disorder, described in humans as hyperornithinemia, hyperammonemia, and homocitrullinuria (HHH) syndrome. The disorder is thought to be caused by a defective mitochondrial transporter protein, such that ornithine, required for complete urea synthesis, is deficient, thus causing increases in blood ammonia and ornithine concentrations.

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