Peer-reviewed veterinary case report
Hereditary methemoglobinemia causing blue gums in male cats
By Jaffey, Jared A et al.·Published in Journal of veterinary internal medicine·2019·Department of Veterinary Medicine and Surgery·View original on PubMed →
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Original publication title: Clinical, metabolic, and genetic characterization of hereditary methemoglobinemia caused by cytochrome breductase deficiency in cats.
- Species:
- cat
Plain-English summary
Two male cats were observed for three years with a condition called methemoglobinemia, which caused their blood to appear dark and resulted in persistent cyanosis (bluish discoloration of the skin). Despite normal heart and lung evaluations, one cat struggled with exercise intolerance, while the other developed anemia and sadly passed away due to other health issues. Genetic testing revealed two new mutations linked to this condition, which could affect the production of a crucial enzyme in their blood. Unfortunately, the exact prevalence of this genetic issue in cats is still unknown.
People also search for: cat cyanosis causes · cat exercise intolerance · hereditary blood disorders in cats · cat anemia treatment · methemoglobinemia in cats
Abstract
Two non-pedigreed male castrated cats had persistent cyanosis over a 3-year observation period. Clinical cardiopulmonary evaluations did not reveal abnormalities, but the blood remained dark after exposure to air. Erythrocytic methemoglobin concentrations were high (~40% of hemoglobin) and cytochrome breductase (CYB5R) activities in erythrocytes were low (≤15% of control). One cat remained intolerant of exertion, and the other cat developed anemia and died due to an unidentified comorbidity. Whole-genome sequencing revealed a homozygous c.625G>A missense variant (B4:137967506) and a c.232-1G>C splice acceptor variant (B4:137970815) in CYB5R3, respectively, which were absent in 193 unaffected additional cats. The p.Gly209Ser missense variant likely disrupts a nicotinamide adenine dinucleotide (NADH)-binding domain, while the splicing error occurs at the acceptor site for exon 4, which likely affects downstream translation of the protein. The 2 novel CYB5R3 variants were associated with methemoglobinemia using clinical, biochemical, genomics, and in silico protein studies. The variant prevalence is unknown in the cat population.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/31650629/