Open AccessLong‐term Treatment with Methylene Blue in a Dog with Hereditary Methemoglobinemia Caused by Cytochrome b5 Reductase Deficiency
Author(s) -
Jaffey J.A.,
Harmon M.R.,
Villani N.A.,
Creighton E.K.,
Johnson G.S.,
Giger U.,
Dodam J.R.
Publication year - 2017
Publication title -
journal of veterinary internal medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.356
H-Index - 103
eISSN - 1939-1676
pISSN - 0891-6640
DOI - 10.1111/jvim.14843
Subject(s) - methemoglobinemia , methemoglobin , medicine , heinz body , methylene blue , lethargy , anesthesia , cytochrome c oxidase , endocrinology , hemoglobin , biochemistry , enzyme , biology , photocatalysis , catalysis
A juvenile male mixed breed dog was presented for lethargy, exercise intolerance, and aggression when touched on the head. Cyanosis, tachycardia, and tachypnea were observed and persisted during oxygen supplementation. Arterial blood gas analysis by co‐oximetry identified an increased methemoglobin concentration (27%; normal, <2%) with normal arterial oxygen tension. The methemoglobinemia and associated clinical signs resolved after administration of methylene blue (1 mg/kg) IV , and the dog was discharged. The affected dog's whole‐genome sequence contained 2 potentially causal heterozygous CYB 5R3 missense mutations suggesting that cytochrome b5 reductase deficiency was responsible for the methemoglobinemia. This hypothesis was confirmed by enzyme analysis that identified cytochrome b5 reductase activity in the affected dog's erythrocytes to only approximately 6% of that in a control sample. Clinical signs recurred 11 days after discharge but normalized and the methemoglobin concentration decreased with methylene blue administration PO (1.5 mg/kg, initially daily and then every other day).