Severe lactic acidosis associated with a suspected succinic semialdehyde dehydrogenase (SSADH) deficiency in a young Chihuahua dog

This report describes a case of severe lactic acidosis associated with a suspected succinic semialdehyde dehydrogenase (SSADH) deficiency in a 5-month-old Chihuahua. The dog was presented for obtundation and “drunk-like” behavior of 1 month duration. Venous blood gas analysis revealed a severe lactic acidosis (blood pH 6.938; reference interval 7.35-7.45; lactate concentration 18.27 mmol/L; reference interval 0.8-2.0 mmol/L). As other causes of encephalopathy and hyperlactatemia were ruled out, an inborn error of lactate metabolism was suspected. Quantitative organic acid analysis showed marked elevations of urine lactic acid, pyruvic acid and gamma-hydroxybutyric acid (or 4-hydroxybutyric acid) concentrations. Activity level of SSADH, measured in the dog’s cultured lymphoblasts, was 30% of that recorded in three healthy dogs, suggesting SSADH deficiency. The dog initially responded to treatment, but eventually deteriorated, and was euthanized. Organic acidurias are being increasingly recognized in veterinary medicine; however SSADH deficiency has never been reported in dogs. Early identification of inherited organic aciduria in domestic animals might facilitate prompt, appropriate treatment, and potentially facilitate modelling of corresponding human pathologies.