A fatal, neurologic disease of Gordon Setters called DUNGd by breeders was first reported in the veterinary literature in 2000 as an autosomal recessive trait. Gait and postural abnormalities and progressive weakness begin at 3-4 weeks of age, progressing to visual deficits and recumbency by 5-6 weeks of age. Serum chemistries and CSF analysis are normal and only subtle and non-specific histopathologic findings are observed at necropsy. Urine samples from three affected puppies were assayed by gas chromatography/mass spectroscopy for organic acids. A distinct pattern of elevated glycine conjugates (3-methylcrotonylglycine, 2methylbutyrlglycine, hexanoylglycine) was observed in all three samples. Urine from one obligate carrier parent and one clinically normal littermate showed a similar pattern and urine samples from one obligate carrier parent and two clinically normal littermates were normal. Based on the human literature the organic acid findings were most consistent with a mutation in the biotinidase (BTD) or holocarboxylase synthase (HLCS) genes. Primary methylcrotonyl CoA carboxylase (MCC) deficiency has also been reported albeit with much milder clinical signs. Coding regions of the BTD and HLCS genes have been sequenced and no significant mutations identified. Sequencing of the MCC gene is pending.