Clinical and laboratory findings in border collies with presumed hereditary juvenile cobalamin deficiency.

Juvenile cobalamin deficiency is a rare disease in border collies and its diagnosis requires a high level of clinical suspicion. The goal of this study was to increase awareness of this disease by describing the clinical and laboratory findings in four young border collies with inherited cobalamin deficiency. The median age of the dogs was 11.5 mo (range, 8-42 mo), and two of the four dogs were full siblings. Clinical signs included intermittent lethargy (n = 4), poor body condition (n = 4), odynophagia (n = 2), glossitis (n = 1), and bradyarrhythmia (n = 1). Pertinent laboratory abnormalities were mild to moderate normocytic nonregenerative anemia (n = 3), increased aspartate aminotransferase (AST) activity (n = 3), and mild proteinuria (n = 3). All of the dogs had serum cobalamin levels below the detection limit of the assay, marked methylmalonic aciduria, and hyperhomocysteinemia. Full clinical recovery was achieved in all dogs with regular parenteral cobalamin supplementation, and laboratory abnormalities resolved, except the proteinuria and elevated AST activity persisted. This case series demonstrates the diverse clinical picture of primary cobalamin deficiency in border collies. Young border collies presenting with ambiguous clinical signs should be screened for cobalamin deficiency.