Fatal chronic copper-associated hepatitis in a Labrador retriever
Felipe Reggeti, Glenna McGregor, Nick Schrier
Animal Health Laboratory, University of Guelph, Guelph, ON (Reggeti, Schrier); Animal Health Centre, Abbotsford BC (McGregor)
AHL Newsletter 2020;24(3):21.
A 10-year-old female spayed Labrador retriever died 3 days after showing clinical signs consisting of tremors, drooling, mydriasis and profound depression/coma. The owner noted the dog was chewing on grass and roots in the yard. The area had endemic Amanita phalloides and Amanita pantherinoides and this dog had been hospitalized months prior with elevated liver enzymes suspected to be caused by mushroom toxicity.
The body was submitted to the Animal Health Center, Ministry of Agriculture, Abbotsford, BC for postmortem examination. The animal was in good body condition (BCS 3/5) with moderate autolysis and diffuse yellow discoloration (icterus). The abdominal cavity contained approximately 500 mL of clear yellow to blood-tinged fluid. The liver was shrunken, firm, with numerous 1-2 cm diameter nodules, consistent with macronodular cirrhosis (Fig. 1). No intact pieces of mushroom were noted in the gastrointestinal tract.
Histopathology of the liver revealed thick bands of fibrous tissue with mixed inflammatory cells, surrounding and separating variably-sized regenerative nodules and more normal hepatic parenchyma. Centrilobular hepatocellular necrosis was prominent. In a rhodamine red-stained section, large amounts of copper were present in virtually all hepatocytes and Kupffer cells, with larger quantities in centrilobular hepatocytes (Fig. 2).
Liver samples were sent to the Animal Health Laboratory (AHL), University of Guelph for heavy metal screen by inductively coupled plasma mass spectrometry (ICP-MS). The analysis identified: copper (Cu) 1560 ppm (adequate 90 - 300 ppm) and iron (Fe) 1620 ppm (adequate 300-900 ppm) on a dry weight (dw) basis. Based on histopathological evidence of chronic hepatitis with accumulation of Cu in centrilobular areas, identification of toxic levels of Cu (in excess of 1000 ppm dw) and exclusion of infectious diseases, a diagnosis of Cu hepatitis was made. These findings are compatible with the current recommendations for the diagnosis of Cu-associated chronic hepatitis (1).
Copper accumulates in the liver as a result of genetic defects limiting Cu excretion (primary); in association with underlying inflammation, fibrosis or cholestasis (secondary), or due to increased consumption. It has been shown that the pattern of Cu accumulation in primary Cu storage disease is always centrilobular, as noted in this case. Cu levels in these animals are commonly higher than 2000 ppm dw, but may be lower with advanced cirrhosis, as Cu does not accumulate in hyperplastic nodules and fibrous tissue, which can be quite abundant (2). Concomitant high Fe is consistently reported in cases of Cu toxicity. Fe commonly accumulates in the liver in the context of underlying diseases (e.g. inflammation), and it is speculated that hepatic Fe sequestration might contribute to oxidative injury underlying the cell damage in Cu toxicity.
The owner indicated this dog was fed a high Cu diet, which could have been a contributing factor, but the distribution of the lesions and Cu levels are more consistent with a primary storage disorder. Furthermore, the brother of this dog died 8 months prior with elevated liver enzymes of undetermined origin. This could point to a familial genetic mutation resulting in copper accumulation and copper-associated hepatitis in both dogs. Recent evidence suggests that mutations in the gene coding for the transporter ATP7B is associated with high levels of Cu in the liver of Labrador retrievers, as seen in humans with Wilson’s disease (3). AHL
Figure 1. Gross image of the liver showing macro nodular appearance (cirrhosis).
Figure 2. Abundant copper accumulation (red granules) in hepatocytes and Kupffer cells. Qualitative copper score 4/5. Rhodamine red. 200X
References
1. Webster CR et al. ACVIM consensus statement on the diagnosis and treatment of chronic hepatitis in dogs. J Vet Intern Med 2019;33:1173–1200.
2. Smedley R et al. Copper-associated hepatitis in Labrador retrievers. Vet Pathol 2009;46:484–490.
3. Pindar S, Ramirez C. Predicting copper toxicosis: relationship between the ATP7A and ATP7B gene mutations and hepatic copper quantification in dogs. Hum Genet 2019;138(5):541-546.