JPC SYSTEMIC PATHOLOGY
Signalment (JPC #1783194): 3-year-old female Bedlington terrier
HISTORY: This dog presented with lethargy, anorexia, vomiting, and icterus.
HISTOPATHOLOGIC DESCRIPTION: Liver: Affecting approximately 30% of the section, centrilobular hepatocytes are separated and surrounded by, or lost and replaced by nodular aggregates of: macrophages, lymphocytes, fewer non-degenerate neutrophils and plasma cells, small amounts of eosinophilic cellular and karyorrhectic debris (necrosis); surrounded by: eosinophilic fibrillar material (fibrin), increased clear space (edema) and scattered reactive fibroblasts with fibrous connective tissue (fibrosis) that often bridges to other central venous areas or occasionally to portal areas. Adjacent hepatocytes are multifocally swollen with pale eosinophilic, finely vacuolated cytoplasm (degeneration) or are individualized, angular with intensely eosinophilic cytoplasm and pyknotic nuclei (necrosis). Macrophages (within areas of inflammation), Kupffer cells (within sinusoids), and hepatocytes frequently contain either intracytoplasmic brown to gray granular pigment (ceroid or copper) or golden to dark brown granular pigment (bile or hemosiderin). Multifocally scattered bile canaliculi contain variably-sized linear plugs of green-brown bile (cholestasis). Multifocally, within centrilobular and portal areas, there are scattered ectatic lymphatics often associated with areas of inflammation.
D-T05B: Rhodanine: Primarily within inflammatory foci and scattered throughout the remainder of the section, hepatocytes, macrophages, and Kupffer cells in sinusoids are distended by intracytoplasmic red globular pigment (copper).
MORPHOLOGIC DIAGNOSIS: Liver: Hepatocellular degeneration, necrosis and loss, centrilobular, chronic, diffuse, marked, with lymphohistiocytic hepatitis, cholestasis, fibrosis, and hepatocellular and histiocytic copper accumulation, Bedlington terrier, canine.
CONDITION: Inherited copper toxicosis of Bedlington terriers
- Copper plays a role in the following biological processes:
- Mitochondrial respiration via cytochrome C oxidase
- Connective-tissue maturation cross-linking via lysyl oxidase
- Antioxidant defense viasuperoxide dismutase
- Melanin synthesis viatyrosinase
- Iron metabolism viaceruloplasmin
- Neurotransmitter biosynthesis via dopamine β hydroxylase
- Excess copper mediates free-radical production causing cellular damage thru oxidation reactions by initially reducing available glutathione (antioxidant) resulting in damage to lipids, proteins, and nucleic acids
- After saturation of lysosomes, copper accumulates in the nucleus and damages DNA with subsequent apoptosis (likely due to induction of p53 protein)
- Mechanisms of hepatic copper toxicosis:
- Primary metabolic defect in hepatic copper metabolism
- Altered hepatic biliary excretion of copper
- Excess dietary intake of copper
- Autosomal recessive disorder of copper metabolism due to exon 2 deletion of MURR1 gene (also referred to as COMMD1 gene) causing progressive hepatic copper accumulation with age, leading to progressive fatal hepatitis or chronic hepatitis with cirrhosis
- Only Bedlington terriers have been shown to accumulate copper throughout life
- Dietary copper z> taken up by SI enterocytes via divalent metal transporters (DMT1) and copper transporter 1 (Ctr1) > portal blood bound to ceruloplasmin,transcuprein, oralbumin > liver > sequestered in metallothionein or glutathione in hepatocytes > excretion into bile (major route) or blood regulated by chaperones, copper-transporting ATPase ATP7A
- Serum copper exists in two pools:
- Exchangeable pool - loosely bound to transcuperin (80%), albumin, or other low molecular weight molecules en route to the liver
- Tightly bound - copper exported from the liver in the form of ceruloplasmin
- Affected dogs have reduced copper excretion into the bile causing increased hepatic and renal copper
- Copper accumulates in almost all hepatocellular organelles; the majority is bound to metallothionein in lysosomes
- Copper does not cause hepatitis in Bedlington terriers until concentrations reach 2000 ppm dry weight (dw)
- Normal is <400 ppm dw
- Hepatic copper levels may reach 12,000 ppm dw in BT with homozygous recessive trait
- After reaching peak levels at 6 years of age, there is a trend of decreasing hepatic copper levels possibly due to: 1) cirrhosis, which dilutes copper since scar tissue does not contain copper, 2) hepatocyte adaptation, or 3) normal homeostatic regulatory mechanisms
- Chronic cholestasis may also result in elevated copper levels in the liver
- Serum copper exists in two pools:
TYPICAL CLINICAL FINDINGS:
- Ascites, CNS signs, depression, weight loss, vomiting; jaundice inconsistently
- Hemolysis is rare
- Serum copper level is normal regardless of the hepatic copper concentration
TYPICAL GROSS FINDINGS:
- Fibrotic, pale liver that becomes nodular (cirrhotic) as disease progresses
- Sheep that die of acute hemolytic syndrome secondary to chronic copper toxicity:
- Red discoloration due to hemoglobin; may also be brown due to methemoglobin
- Dark red to black kidneys and dark red urine
- Hepatomegaly with yellow discoloration or atrophic and fibrotic if preceded by longstanding liver injury
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Lesions (necrosis and hepatitis) begin in centrilobular area (zone 3) then spread and increase in size as the disease progresses and are associated with copper-laden hepatocytes
- Progresses to portal and diffuse fibrosis and chronic-active periportal hepatitis, with macronodular regeneration (cirrhosis)
- Golden brown to amphophilic, occasionally refractile granules in hepatocytes and Kupffer cells (autophagolysosomes that contain ferric iron and copper)
- Cu < 2000 ppm: In electron dense lysosomes; minimal cytoplasmic changes
- Cu > 2000 ppm: Also in the nucleus; mild nuclear degeneration
- Cu > 7000 ppm: Accumulates (in descending order) in lysosomes, nucleus, and cytoplasm; shrunken hepatocytes with electron dense organelles, nuclei contracted and misshapen with chromatin condensation and fragmentation, and apoptotic bodies in sinusoids
ADDITIONAL DIAGNOSTIC TESTS:
- Special stains (rubeanic acid, rhodanine) can identify copper-laden lysosomes at concentrations > 400 ppm dw
- Atomic absorption analysis to measure hepatic copper concentration
- Blood or kidney copper levels in sheep with suspect chronic copper toxicity
For chronic hepatotoxicity in dogs:
- Idiopathic chronic active hepatitis: Periportal (zone 1) or random small foci of inflammation and piecemeal necrosis; periportal copper accumulation (<2000ppm) secondary to inflammatory disease; no cholestasis; micronodular regeneration; hyperglycemia; especially middle-aged, females
- Drug-induced hepatopathy:
- Anticonvulsants - rarely progresses to nodular fibrosis
- Sulfonamides - hepatitis and hepatic necrosis; Doberman Pinschers especially sensitive
- Mebendazole - centrilobular necrosis
- Indospicine poisoning from ingestion of legumes: Centrilobular and piecemeal necrosis with accumulation of ceroid pigment in macrophages
- Animals deficient in vitamin E or molybdenum are especially susceptible to acute copper poisoning
- Chronic copper toxicosis in sheep:
- May result from:
- Excessive copper intake –water/pasture/feed
- Increased availability of dietary copper often due to low levels of dietary molybdenum – molybdenum forms insoluble complexes with copper in the gut and liver, making the copper inert
- Other hepatotoxins – most commonly pyrrolizidine alkaloids (from Heliotropium or Echium) and phomopsin from lupins
- Copper tends to accumulate in the liver of sheep and they have a low rate of excretion into bile, increasing their susceptability to copper toxicity
- North Ronaldsay sheep especially susceptible – they eat a diet of seaweed (low in copper and molybdenum but high in zinc), zinc can also interfere with copper uptake, and when these sheep go back on a normal diet they quickly develop copper toxicity
- Rate of hepatocellular loss exceeds capacity of the liver to phagocytize cell debris > plasma copper levels rise > damage circulating erythrocytes > intravascular hemolysis and anemia > increased hepatocellular damage > progressive intravascular hemolysis and liver failure > hemoglobinuric nephrosis > death
- Blood or kidney copper levels give a truer indication of a prior hemolytic crisis caused by chronic copper poisoning than elevation of liver copper
- Chronic copper poisoning in pigs and cattle:
- Especially common in calves, associated with acute intravascular hemolysis
- More hepatic evidence of chronic damage with extensive portal fibrosis and biliary hyperplasia within triads
- Acute copper poisoning:
- Most often seen in ruminants after administration of single large doses of copper (oral or parenteral)
- Develop severe gastroenteritis, abdominal pain, diarrhea, and dehydration
- Liver lesions vary with chronicity of exposure from acute centrilobular necrosis to cholangiohepatitis with periportal fibrosis
- West Highland white terriers:
- Inherited copper storage disease; accumulates in centrilobular areas (zone 3)
- No correlation between age and hepatic copper levels (nonprogressive), and hepatocellular damage is detected at lower concentrations of copper (< 2000 ppm dw)
- Other dog breeds: Excess hepatic copper causes centrilobular acute hepatic necrosis, subacute hepatitis, chronic hepatitis, and cirrhosis
- Causes may include:
- Metabolic defects (new variant inherited primary toxicosis) – Doberman pinschers and Dalmatians
- Cholestasis (secondary) – Skye terrier hepatitis (intracanalicular)
- High copper levels in commercial dog food
- Also reported in cocker spaniels, German shepherd dogs, keeshonds, Kerry blue terriers, Labrador retrievers, old English sheepdogs and Samoyeds; associated with renal tubular dysfunction in Labrador retrievers
- Causes may include:
- Ferrets: Chronic portal hepatitis and hepatic necrosis reported in two sibling silver ferrets with high liver copper levels; genetic predisposition considered
- Cats: Chronic hepatitis suggestive of primary copper storage disease and acute hepatitis secondary to increased copper levels
- Single reports of copper toxicosis in New Zealand white rabbits and a sugar glider
- Animal models: Long-Evans cinnamon rat and toxic milk mice – genetic defect similar to Wilson’s disease in humans
- Brown DL, Van Wettere AJ, Cullen JM. Hepatobiliary system and exocrine pancreas. In: McGavin MD, Zachary JF, eds. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:440, 457.
- Cullen JM, Stalker MJ. Liver and biliary system. In: Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier, 2016:302-305, 342-343.
- Hurwitz BM, Center SA, Randolph JF, McDOnough SP, Warner KL, et al. Presumed primary and secondary hepatic copper accumulation in cats. J Am Vet Med Assoc. 2014; 24(1):68-77.
- LaDouceur EEB, Wynne J, Garner MM, Nyaoke A, Keel MK. Lesions of copper toxicosis in captive marine invertebrates with comparisons to normal histology. Vet Pathol. 2016; 53(3):648-658.
- Langlois DK, Smedley RC, Schall WD, Kruger JM. Acquired proximal renal tubular dysfunction in 9 Labrador retrievers with copper-associated hepatitis. J Vet Intern Med. 2013: 27(3):491-499.
- Ramirez CJ, Kim DY, Hanks BC, Evan TJ. Copper toxicosis in New Zealand white rabbits (Oryctolagus cuniculus). Vet Pathol. 2013;50(6):1135-1138.
- van den Ingh TSGAM, Van Winkle T, Cullen JM, Charles JA, Desmet VJ. Morphological classification of parenchymal disorders of the canine and feline liver, 2. Hepatocellular death, hepatitis and cirrhosis. In: WSAVA Standards for clinical and histological diagnosis of canine and feline liver disease. Philadelphia, PA: Saunders Elsevier; 2006:95-96.
- van Winkle T, Cullen JM, van den Ingh TSGAM, Charles JA, Desmet VJ. Morphological classification of parenchymal disorders of the canine and feline liver, 3. Hepatic abscesses and granulomas, hepatic metabolic storage disorders and miscellaneous conditions. In: WSAVA Standards for clinical and histological diagnosis of canine and feline liver disease. Philadelphia, PA: Saunders Elsevier; 2006:106-110.
- Wynne J, LaDouceur EEB, Ryan H. Clinical copper toxicosis in a large mixed group of marine invertebrates. J Zoo Wildl Med. 2015; 46(3):601-604.