Daily oral cyanocobalamin supplementation in Beagles with hereditary cobalamin malabsorption (Imerslund-Grasbeck syndrome) maintains normal clinical and cellular cobalamin status

Background: Efficacy of PO cobalamin (Cbl) supplementation in dogs with hereditary Cbl malabsorption (Imerslund-Grasbeck syndrome, IGS) is unknown. Objectives: To evaluate PO Cbl supplementation in Beagles with IGS previously treated parenterally. We hypothesized that 1 mg cyano-Cbl daily PO would maintain clinical and metabolic remission. Animals: Three client-owned Beagles with IGS and 48 healthy control dogs. Methods: Prospective study. Daily PO cyanocobalamin (cyano-Cbl; 1 mg) supplementation was monitored for 13 (2 dogs) and 8 months (1 dog). Health status was assessed by owner observations. Methylmalonic acid (MMA)-to-creatinine concentrations were measured using an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-TMS) method on urine samples collected monthly. Concurrent measurements of serum MMA concentration (n = 7; UPLC-TMS) were available for 1 dog. Results: All dogs remained in excellent health during PO supplementation. Urine MMA remained consistently low in 2 dogs (median, 2.5 mmol/mol creatinine; range, 1.2-9; healthy dogs [n = 30]. median, 2.9 mmol/mol creatinine; range, 1.3-76.5). Urine MMA ranged from 38.9-84.9 mmol/mol creatinine during the first 6 months in 1 dog already known to excrete comparable amounts when supplemented parenterally. Brief antibiotic treatment for an unrelated condition after 6 months resulted in low urine MMA (median, 2.8 mmol/mol creatinine; range, 1.9-4.8) for the next 7 months. All concurrent serum MMA concentrations (median, 651 nmol/L; range, 399-919) before and after month 6 were within the established reference interval (3934476 nmol/L; n = 48). Conclusions and Clinical Importance: One milligram of cyano-Cbl daily PO appears efficacious for maintaining normal clinical status and normal cellular markers of Cbl metabolism in Beagles with IGS.