Jaffey J A, Harmon M R, Villani N A, Creighton E K, Johnson G S, Giger U, Dodam J R
Department of Veterinary Medicine and Surgery, Veterinary Health Center, University of Missouri, Columbia, MO.
Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO.
J Vet Intern Med. 2017 Nov;31(6):1860-1865. doi: 10.1111/jvim.14843. Epub 2017 Sep 29.
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 CYB5R3 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).
一只幼年雄性混种犬因嗜睡、运动不耐受以及头部被触摸时出现攻击行为前来就诊。观察到该犬有发绀、心动过速和呼吸急促症状，且在吸氧过程中持续存在。通过共血氧测定法进行的动脉血气分析显示，高铁血红蛋白浓度升高（27%；正常范围，<2%），而动脉血氧张力正常。静脉注射亚甲蓝（1 mg/kg）后，高铁血红蛋白血症及相关临床症状得到缓解，该犬出院。患病犬的全基因组序列包含2个潜在的致病性杂合CYB5R3错义突变，提示细胞色素b5还原酶缺乏是导致高铁血红蛋白血症的原因。酶分析证实了这一假设，该分析确定患病犬红细胞中的细胞色素b5还原酶活性仅约为对照样本的6%。出院11天后临床症状复发，但口服亚甲蓝（1.5 mg/kg，最初每日一次，随后隔日一次）后症状恢复正常，高铁血红蛋白浓度降低。
