A 4-year-old, spayed female domestic shorthair presented with lateral recumbency and stupor. She had a recent history of weakness, imbalance, anorexia, and mental dullness associated with consumption of a protein-rich cat food.The cat had presented with similar signs twice previously, at 11 months of age. Laboratory workup at that time included urinalysis and bile acid testing, which were normal.Because her clinical signs seemed to worsen after consuming a regular adult cat food, she had been fed a low-protein cat food for 3 years.Two months before the current presentation, she was switched to the protein-rich cat food after refusing to eat the low-protein food.The patient had unexplained metabolic acidosis and ketonuria (there was no evidence of diabetic ketoacidosis or lactic acidosis). Quantitative organic acid analysis of urine revealed significant elevations, while serum cobalamin concentration was extremely low (< 100 ng/L; reference range, 290 to 1499 ng/L).The patient died several hours after presentation; the diagnosis was severe organic acidemia secondary to low cobalamin levels, which probably resulted from an inborn error of cobalamin absorption.

COMMENTARY: Cats presenting with unexplained metabolic acidosis and ketonuria should be evaluated for possible organic acidemia associated with an inborn error of metabolism. Serum cobalamin (vitamin B12) levels should be checked, as deficiencies may cause accumulation of organic acids in the blood and urine.This cat's history of similar neurologic signs at an early age, the association with consumption of protein rich cat food, and low serum cobalamin suggested an inborn error of cobalamin absorption. Early identification of inherited conditions such as the one described in this report may permit successful lifetime treatment.

Note: Information on serum cobalamin testing is available through Texas A&M College of Veterinary Medicine:www.cvm.tamu.edu/gilab (979 862-2861). Information on testing for urinary methyl malonic acid is available through the Metabolic Genetic Disease Testing Laboratory of the School of Veterinary Medicine at the University of Pennsylvania, PennGen:www.vet.upenn.edu/penngen (215 898-8894).

Organic acidemia in a young cat associated with cobalamin deficiency.Kelmer E, Shelton GD,Williams DA, et al. J VET EMERG CRIT CARE 17:299-304, 2007.