METHYLMALONIC AND MALONIC ACIDURIA IN A DOG WITH PROGRESSIVE ENCEPHALOMYELOPATHY

A 12 week old female Labrador retriever dog with signs of progressive diffuse degeneration of the brain and spinal cord was found to have me thlymalonic and malonic aciduria. Over a 5 month period, the dog devel oped neurologic signs compatible with disease of the central nervous s ystem with predominant diffuse cerebral and right lateralizing brainst em deficits. Gross pathological examination of the brain showed that t he lateral, third, and fourth ventricles of the brain were markedly en larged and associated with white and grey matter atrophy. Syringomyeli a and hydromyelia of the central canal into the dorsal funiculus of th e spinal cord beginning at the level of the cervical intumescence and extending to the lumbar intumescence was also present. Significant bio chemical abnormalities include methylmalonic and malonic aciduria, mil d lactic and pyruvic aciduria. There was also accumulation of citric a cid cycle intermediates including succinic, aconitic, and fumaric acid s. Disordered fatty acid oxidation was suggested by increased excretio n of adipic, ethylmalonic, suberic and sebacic acids. Neither ketoacid osis nor hyperammonemia were present, and serum cobalamin levels were normal. Overall, this dog demonstrates an inborn error of metabolism r esulting in abnormal organic acid accumulation associated with a neuro degenerative disease.