BackgroundIn veterinary medicine, congenital methemoglobinemia associated with nicotinamide adenine dinucleotide (NADH)‐cytochrome b5 reductase (b5R) deficiency is rare. It has been reported in several breeds of dogs, but little information is available about its etiology.ObjectivesTo analyze the NADH‐cytochrome b5 reductase gene, CYB5R3, in a Pomeranian dog family with methemoglobinemia suspected to be caused by congenital b5R deficiency.AnimalsThree Pomeranian dogs from a family with methemoglobinemia were analyzed. Five healthy beagles and 5 nonrelated Pomeranian dogs without methemoglobinemia were used as controls.MethodsMethemoglobin concentration, b5R activity, and reduced glutathione (GSH) concentration were measured, and a turbidity index was used to evaluate Heinz body formation. The CYB5R3 genes of the affected dog and healthy dogs were analyzed by direct sequencing.ResultsMethemoglobin concentrations in erythrocytes of the affected dogs were remarkably higher than those of the control dogs. The b5R activity of the affected dogs was notably lower than that of the control dogs. DNA sequencing indicated that this Pomeranian family carried a CYB5R3 gene missense variant (ATC→CTC at codon 194) that resulted in the replacement of isoleucine (Ile) by leucine (Leu).Conclusions and Clinical ImportanceThis dog family had familial congenital methemoglobinemia caused by b5R deficiency, which resulted from a nonsynonymous variant in the CYB5R3 gene. This variation (c.580A>C) led to an amino acid substitution (p.Ile194Leu), and Ile194 was located in the proximal region of the NADH‐binding motif. Our data suggested that this variant in the canine CYB5R3 gene would affect function of the b5R in erythrocytes.

Babesia rossi infection has been reported to be associated with the high prevalence of pancreatitis in dogs. In this study, we retrospectively investigated whether pancreatitis occurs in B. gibsoni-infected dogs. The clinical manifestations, and hematological and serum biochemical examination results, including canine pancreatic-specific lipase (cPL), in 20 B. gibsoni-infected dogs were analyzed. The cPL concentration exceeded 400 µg/l in only 2 dogs, and they were suspected of having pancreatitis. Although the cPL concentration did not correlate with the degree of anemia or the level of parasitemia, it correlated with the band neutrophil count, platelet count, and blood urea nitrogen (BUN) level. Our study suggested that the prevalence of pancreatitis is lower among B. gibsoni-infected dogs than B. rossi-infected dogs.

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