Indian childhood cirrhosis in an American child

Application of exome sequencing in the search for genetic causes of rare disorders of copper metabolism

The genetic defect in a number of rare disorders of metal metabolism remains elusive. The limited number of patients with these disorders impedes the identification of the causative gene through positional cloning, which requires numerous families with multiple affected individuals. However, with next-generation sequencing all coding DNA (exomes) or whole genomes of patients can be sequenced to identify genes that are consistently mutated in patients. With this strategy only a limited number of patients and/or pedigrees is needed, bringing the elucidation of the genetic cause of even very rare diseases within reach. The main challenge associated with whole exome sequencing is the identification of the disease-causing mutation(s) among abundant genetic candidate variants. We describe several strategies to manage this data wealth, including comparison with control databases, increasing the number of patients and controls, and reducing the genomic region under investigation through homozygosity mapping. In this review we introduce a number of rare disorders of copper metabolism, with a suspected but yet unknown monogenetic cause, as an attractive target for this strategy. We anticipate that use of these novel techniques will identify the basic defect in the disorders described in this review, as well as in other genetic disorders of metal metabolism, in the next few years.

Immunohistochemical analysis of Mallory bodies in Wilsonian and non-Wilsonian hepatic copper toxicosis

Patients with Wilson's disease (WD), Indian childhood cirrhosis (ICC), and idiopathic copper toxicosis (ICT) develop severe liver disease morphologically characterized by ballooning of hepatocytes, inflammation, cytoskeletal alterations, and Mallory body (MB) formation, finally leading to mostly micronodular cirrhosis. The pathogenesis of MBs in copper toxicosis is still unresolved. Immunohistochemical analysis of MBs in different types of copper intoxication revealed that keratin, p62, and ubiquitin are integral components. Thus MBs associated with copper intoxication resemble those present in alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH). p62 is a multifunctional immediate early gene product that, on the one hand, is involved in stress-induced cell signaling (particularly that of oxidative stress) by acting as an adapter protein linking receptor-interacting protein (RIP) with the atypical protein kinase C. On the other hand, p62 binds with high affinity to polyubiquitin and ubiquitinated proteins. In conclusion, p62 accumulation in WD, ICC, and ICT and deposition in MBs indicates a central role of protein misfolding induced by oxidative stress in copper-induced liver toxicity. By sequestering potentially harmful misfolded ubiquitinated proteins as inert cytoplasmic inclusion bodies (e.g., as MBs), p62 may be a major player in an important cellular rescue mechanism in oxidative hepatocyte injury.

Copper metabolic defects and liver disease: environmental aspects

Copper (Cu) is an essential trace element for many biological processes. Cu homeostasis is generally well maintained by inbuilt controls in intestinal absorption, biliary excretion and intrahepatic storage. Copper deficiency disorders are rare. Acute Cu toxicity occurs occasionally in accidental poisoning with Cu sulfate. Chronic Cu toxicity in the form of liver cirrhosis and damage to other organs is seen classically in Wilson's Disease (genetic abnormality of Cu metabolism) and in the presumed environmental disorder Indian Childhood Cirrhosis (ICC). The clinical, epidemiological and treatment aspects of ICC are described. The evidence linking ICC to environmental Cu is (i) greatly increased hepatic Cu; (ii) early introduction of Cu contaminated milk boiled or stored in brass vessels; (iii) dramatic decline in ICC throughout the country coincident with change in feeding vessels; and (iv) continued long-term remission in d-penicillamine-treated patients after withdrawal of the drug. The nature and role of a second factor in the causation of ICC remains unclear, although a genetic predisposition is strongly suspected. Scattered reports of an ICC-like illness from the West (Idiopathic Cu Toxicosis, Endemic Tyrolean Infantile Cirrhosis), suggest that different mechanisms (environmental, genetic or both) can lead to the same end stage liver disease-'ecogenetic' disorders.

Mechanisms of liver injury relevant to pediatric hepatology

Hepatocyte injury and necrosis from many causes may result in pediatric liver disease. Influenced by other cell types in the liver, by its unique vascular arrangements, by lobular zonation, and by contributory effects of sepsis, reactive oxygen species and disordered hepatic architecture, the hepatocyte is prone to injury from exogenous toxins, from inborn errors of metabolism, from hepatotrophic viruses, and from immune mechanisms. Experimental studies on cultured hepatocytes or animal models must be interpreted with caution. Having discussed general concepts, this review describes immune mechanisms of liver injury, as seen in autoimmune hepatitis, hepatitis B and C infection, the anticonvulsant hypersensitivity syndrome, and autoimmune polyendocrinopathy. Of the monogenic disorders causing significant liver injury in childhood, alpha-1 antitrypsin deficiency and Niemann-Pick C disease demonstrate the effect of endoplasmic or endosomal retention of macromolecules. Tyrosinemia illustrates how understanding the biochemical defect leads to understanding cell injury, extrahepatic porphyric effects, oncogenesis, pharmacological intervention, and possible stem cell therapy. Pathogenesis of cirrhosis in galactosemia remains incompletely understood. In hereditary fructose intolerance, phosphate sequestration causes ATP depletion. Recent information about mitochondrial disease, NASH, disorders of glycosylation, Wilson's disease, and the progressive familial intrahepatic cholestases is discussed.

Environmental copper: its dynamics and human exposure issues

This article provides an overview of the environmental patterns and dynamics of copper from the perspective of issues that affect our ability to examine current human exposures. It presents selected summary information on the levels of copper found in various media and exposure pathways from a variety of information sources, and discusses the breadth and the limitations of this information. The analysis presented focuses on the ability to provide quantitative values for both external metrics of exposures (microenvironmental levels) and internal biological markers of exposure. The status of the current information on environmental copper is placed within a conceptual framework that can be used to identify data gaps, assess the utility of current biological markers of exposure, and examine the need for systematic and consistent data-gathering studies to improve our ability to complete exposure assessments. A primary concern is the exposure to copper through potable water supplies; this is considered within a framework that examines copper levels and distribution in food, soil, air and sediments, as well as the levels found in biological media such as urine, blood, and hair. An existing water consumption model for copper and associated exposure factors is briefly discussed. This type of model will eventually be valuable within a total exposure analysis modeling framework that can consider and prioritize exposures from multiple routes and differentiate levels of concern for both excesses and deficiencies in exposure, an important issue, since copper is an essential nutrient. Finally, this review attempts to examine the needs for better information using as a basis the concerns briefly mentioned in the recent NRC report "Copper in Drinking Water" (National Research Council, 2000).

Indian childhood-like cirrhosis in three Saudi Arabian siblings

Three Saudi siblings, two girls and one boy, presented at the ages of 7, 6 and 2.5 years, respectively, and were diagnosed as having features of Indian childhood cirrhosis (ICC). The two girls presented at a late stage of the disease and the boy was diagnosed during routine examination of the family. The initial presenting complaint was abdominal distention and pruritus. All three had a rapid and fatal course. There was no evidence of increased copper ingestion by the families, supporting the suggestion of a hereditary metabolic role in the aetiology of ICC. As far as we are aware, this is the first report of ICC in Saudi Arabian children.

Familial clustering of infantile cirrhosis in Northern Germany: A clue to the etiology of idiopathic copper toxicosis

Two cases of infantile liver cirrhosis of unknown origin occurred in a circumscribed rural area of Northern Germany. Both children had increased dietary copper exposure. The search for additional cases of what appeared to be idiopathic copper toxicosis (ICT) revealed a cluster of affected infants in this region, raising questions about the relative importance of genetic and environmental factors that are considered to be etiologic. We gathered clinical and pathologic data concerning the patients, analyzed the pedigrees of affected families, and searched for possible environmental factors contributing to the pathologic process. We encountered 8 cases of infantile liver cirrhosis in 5 families in Emsland, a circumscribed and predominantly rural area of Northern Germany; ICT was definitely proven in 2 cases. Clinical presentation and liver pathology in 6 additional cases were consistent with the diagnosis of ICT. Pedigrees of affected families revealed complex relationships with occasional consanguinity of parents, suggesting autosomal recessive inheritance. The households were served by private wells with water of low pH flowing through copper pipes, suggesting the possibility of increased alimentary copper exposure. These findings support earlier conclusions that ICT develops when an infant with a genetic predisposition is exposed to a copper-enriched diet.

Identification of a novel copper-binding protein from the liver of Indian childhood cirrhosis: purification and physicochemical characterization [corrected]

A novel copper-binding protein was identified in the liver supernatant (100,000 x g) of Indian childhood cirrhosis (ICC), purified to apparent homogeneity and characterized [corrected]. Purified major copper-binding protein (MCuBP) is solely responsible for binding about 35% of the total supernatant copper. Elution profile of ICC liver supernatant on Sephadex G-75 column chromatography showed three peaks. About 60% of the total supernatant copper was resolved in peak II, whereas zinc content was insignificant in this peak. But peak II was almost missing in a gel elution profile of control liver supernatant. The control group included cases of various liver diseases viz. neonatal hepatitis, septicemia, and mixed nodular cirrhosis. Copper-binding proteins of peak II further purified on ion-exchange chromatography and elution profile showed that peak II was a MCuBP with high copper-binding capacity (10 g atoms/mol of native protein). SDS-PAGE of this protein also revealed the existence of a single band with molecular mass of about 50 kD. UV spectra of MCuBP showed the maximal absorbance at 254 nm. Unlike the classical metallothionein, the amino acid composition of MCuBP revealed the presence of aromatic amino acids and higher content of glutamic acid and aspartic acid followed by glycine and serine. The ratio (0.3) of basic amino acids to acidic amino acids strongly indicates that it is an acidic protein. The cysteine content in this protein was insignificant, which further corroborates the possibility that the acidic amino acids might be prominent candidates for binding copper. Thus, the 50-kD MCuBP apparently makes a major contribution to the total copper-binding activity in ICC liver cytosol and may play a significant role in hepatic intracellular copper accumulation.

An animal model for copper-associated cirrhosis in infancy

In Indian childhood cirrhosis (ICC) and related disorders of infancy, hepatic copper overload is associated with cirrhosis. Since copper administration alone has not been shown to induce cirrhosis in animals, synergy between copper and a second hepatotoxin has been suggested. This study investigates the ability of long-term exposure to copper and a pyrrolizidine alkaloid, retrorsine, to produce a model of copper-associated cirrhosis in rats. Groups of rat pups suckled on mothers fed 25 mg/kg diet retrorsine were weaned onto a diet containing 0.5 g/kg diet copper and retrorsine in varying dosage for 13 weeks. Histological similarities between the human disease and rats given copper with retrorsine 5 mg/kg diet included parenchymal destruction, fibrosis, nodular regeneration, and copper accumulation. There were significant histological differences from the human disorder, possibly attributable to inter-species variability or the critical timing or duration of exposure to hepatotoxins in the neonatal period. The hypothesis that ICC results from copper and a second hepatotoxin has not been disproved.

Wilson's disease. Update of a systemic disorder with protean manifestations

In Wilson's disease, a genetic defect in a copper transporter causes defective incorporation of copper into apo-ceruloplasmin and the failure to excrete copper into bile. Copper accumulated in hepatocytes generates damage via reactive oxygen species. Release of copper from necrotic hepatocytes leads to damage of other tissues, including the brain, urinary tract, red blood cells, heart, endocrine glands, skin, pancreas, bones, and joints. Treatment is designed to chelate the excess copper for urinary excretion, prevent copper absorption, and render tissue copper nontoxic. Liver transplantation, with replacement of the defective hepatic gene, may be necessary in some cases.

Different pathomorphologic patterns in exogenic infantile copper intoxication of the liver

Pathomorphology of the liver has been reviewed in 12 German infants with chronic exogenic copper intoxication. In 8 cases severe liver damage with diffuse accumulation of Mallory bodies and liver cell necrosis mimicking florid Indian childhood cirrhosis (ICC) was found. Seven of these children died because of liver failure. One child received liver transplantation at the age of 9 months. In contrast, 4 children with a stable clinical course had a complete micronodular cirrhosis in liver biopsy. The characteristic morphological features of ICC, especially ballooning of liver cells and accumulation of Mallory bodies, were only slightly expressed or even lacking. There was no correlation between the copper content of the liver and the severity of liver damage. The copper concentration varied between 541 micrograms/g dry weight (norm < 50 micrograms/g) and 2.154 micrograms/g dry weight in fatal cases. In surviving infants even higher concentrations of up to 698 micrograms/g fresh weight (norm < 5 micrograms/g), were found. The amount of free cytosolic copper varied between 900-4,900 ng/mg protein (13-70 times of normal). In conclusion, a spectrum of pathomorphological alterations exists in exogenic infantile copper disease which correlates with the clinical outcome in contrast to the copper content of the liver. Copper intoxication of the liver should be of diagnostic concern in any case of unclear micronodular cirrhosis in early infancy.

Copper in infant nutrition: safety of World Health Organization provisional guideline value for copper content of drinking water

BACKGROUND

Copper is an essential nutrient for humans. Recently, a limit of 31.48 micromol/l (2 mg/l) was proposed by the World Health Organization as the provisional guideline value for copper content of drinking water. The objective of the study was to determine the tolerance of chronic exposure to drinking water with low or high copper content in infants.

METHODS

Healthy infants (n = 128) were randomly assigned to receive drinking water with less than 1.57 micromol/l (<0.1 mg/l) (n = 48) or 31.48 micromol/l (2 mg/l) of copper (n = 80) from 3 to 12 months of age. At 6, 9, and 12 months of age, serum concentrations of copper, ceruloplasmin, and superoxide dismutase; erythrocyte metallothionein; bilirubin; transaminases; and gamma-glutamyl transferase were measured.

RESULTS

Small differences in biochemical indexes of copper nutrition were observed between the groups, but there was no evidence of adverse or toxic effects. These findings may be explained by an adaptive response to the higher copper intake, limiting copper absorption, and increasing biliary secretion, as well as by an increase in copper storage. It is also possible that the sensitivity of the biochemical indicators employed to detect differences in copper status is limited.

CONCLUSION

No acute or chronic adverse consequences of consuming water with copper content of 31.48 micromol/l (2 mg/l) were detected in infants during the first year of life. The results support the safety of the World Health Organization's provisional guideline value for copper in drinking water during infancy.

Experimental induction of liver fibrosis in young guinea pigs by combined application of copper sulphate and aflatoxin B1

Aflatoxin B1 alone (0.05 mg resp. 0.037 mg/kg/d), copper alone (6.6 mg/kg/d or 200 mg/l drinking water) or a combination of both was administered orally for 6 months to young guinea pigs from the first/second day of life. In the copper group there were no pathomorphological changes. For the aflatoxin B1 group, liver damage was established. In the combined group, liver injury was more frequent and more severe compared to the aflatoxin B1 group and biliary copper excretion was diminished compared with the copper group. Histologically, only the livers of this group exhibited degeneration, atrophy and steatosis of liver cells, inflammatory processes and a more or less prominent fibrosis. For childhood cirrhosis (ICC and ICT) a combined etiology--a liver damaging agent plus elevated alimentary copper--is a plausible hypothesis.

Retrorsine in breast milk influences copper handling in suckling rat pups

AIMS

To explore the hypothesis that a second xenobiotic agent is required with excess copper to produce Indian Childhood Cirrhosis, this study investigated the effect of the pyrrolizidine alkaloid retrorsine fed to the mother during the suckling period upon the serial changes in neonatal copper status.

METHODS

Female Wistar rats with new-born litters were fed either a control or a retrorsine (50 mg/kg) diet. At 0, 4, 8, 11, 15, 18 and 21 days, pups from each litter were weighed, sacrificed and their livers removed for copper, DNA and metallothionein analysis. Serum samples were assayed for caeruloplasmin oxidase activity and albumin.

RESULTS

1) Higher than adult level of hepatic copper in normal rats which rose post-natally before declining from day 11 after birth, 2) raised hepatic copper concentrations and total copper in the retrorsine group from day 15; levels were higher than adult at birth, 3) reduced serum caeruloplasmin oxidase activity and albumin levels in retrorsine group, but both groups lower than adult, 4) lower hepatic metallothionein levels in retrorsine group, but both groups higher than adult, and 5) reduced liver DNA in the retrorsine group when expressed as total DNA and per gram of tissue. These changes were not secondary to under-nutrition as a small study on under-nourished rat neonates showed that copper handling is not significantly altered when compared to well-nourished rats.

CONCLUSIONS

Retrorsine passing to rat neonates via breast milk causes: 1) the accumulation of hepatic copper, 2) impairment of the rise in serum caeruloplasmin, which could indicate a decline in synthesis or failure of copper incorporation into the apo-protein, 3) a decrease in hepatic metallothionein and serum albumin levels, again suggesting diminished protein synthesis, and 4) reduced hepatic DNA indicative of decreased cell number but increased cell size. Accumulation of liver copper but reduction of copper-binding proteins could result in free copper and explain the synergistic hepatotoxicity of copper and retrorsine.

Chronic copper toxicosis presenting as liver failure in an Australian child

A 20 month old Caucasian male child, after a five week illness, developed liver failure which was successfully treated by liver transplantation. The explanted liver had a histology identical to that seen in Indian childhood cirrhosis and its copper content was increased tenfold. Water used to prepare the child's milk feeds came from a bore via copper conduits and at times contained 120 mumol/l of copper, eight times the recommended maximum for human consumption. Because non-Indian cases of Indian childhood cirrhosis associated with excess copper ingestion are increasingly being recognised, and as early treatment can restore normal liver morphology, we support the use of the previously suggested alternative term for this condition, ie; 'copper-associated liver disease in childhood'. Measurement of hepatic copper concentrations in all children less than six years of age who develop hepatic failure of unknown cause will increase its recognition. On diagnosis sources of increased dietary copper should be investigated to ensure that younger siblings are not similarly exposed.

Endemic Tyrolean infantile cirrhosis: an ecogenetic disorder

BACKGROUND

138 infants and young children died from an endemic infantile liver cirrhosis in a circumscribed rural area of western Austria between 1900 and 1974. Frequency of the disease peaked between 1930 and 1960. It has disappeared from this area since 1974.

METHODS

Clinical and genetic data on the patients was gathered; pedigrees analysed and ethnographic studies and interviews were undertaken.

FINDINGS

The disease, which was clinically and pathologically indistinguishable from Indian childhood cirrhosis and hepatic copper toxicosis, was transmitted by autosomal recessive inheritance. Cow's milk, contaminated with copper from untinned copper or brass vessels, may have contributed to the development of copper toxicosis. Replacement of untinned copper cooking utensils by modern industrial vessels has eradicated the disease.

INTERPRETATION

Our findings strongly suggest that the endemic Tyrolean childhood cirrhosis-and by analogy non-Wilsonian hepatic copper toxicosis occurring elsewhere-is an ecogenetic disorder requiring the involvement of both genetic and environmental factors for the disease to become manifest.

Chronic hepatitis, hepatocyte fragility, and increased soluble phosphoglycokeratins in transgenic mice expressing a keratin 18 conserved arginine mutant

The two major intermediate filament proteins in glandular epithelia are keratin polypeptides 8 and 18 (K8/18). To evaluate the function and potential disease association of K18, we examined the effects of mutating a highly conserved arginine (arg89) of K18. Expression of K18 arg89-->his/cys and its normal K8 partner in cultured cells resulted in punctate staining as compared with the typical filaments obtained after expression of wild-type K8/18. Generation of transgenic mice expressing human K18 arg89-->cys resulted in marked disruption of liver and pancreas keratin filament networks. The most prominent histologic abnormalities were liver inflammation and necrosis that appeared at a young age in association with hepatocyte fragility and serum transaminase elevation. These effects were caused by the mutation since transgenic mice expressing wild-type human K18 showed a normal phenotype. A relative increase in the phosphorylation and glycosylation of detergent solubilized K8/18 was also noted in vitro and in transgenic animals that express mutant K18. Our results indicate that the highly conserved arg plays an important role in glandular keratin organization and tissue fragility as already described for epidermal keratins. Phosphorylation and glycosylation alterations in the arg mutant keratins may account for some of the potential changes in the cellular function of these proteins. Mice expressing mutant K18 provide a novel animal model for human chronic hepatitis, and for studying the tissue specific function(s) of K8/18.

Copper-associated liver disease in childhood

BACKGROUND/AIMS

Indian childhood cirrhosis is associated with high liver copper concentrations and progressive liver disease with a high mortality. Early treatment with penicillamine was found to reduce mortality and reverse liver damage. We aimed to define the clinical features of copper-associated liver disease outwith the Indian subcontinent and encourage the earlier consideration of the syndrome in cryptogenic liver disease.

METHODS

Three European children presented between 10 and 29 months of age with abdominal distension, pyrexia and hepatosplenomegaly. Over 1-5 weeks their condition deteriorated rapidly due to liver failure. Two died within 2 months of onset and one received a successful liver transplant. In two cases consideration of the diagnosis occurred only on examination of the liver after orthotopic liver transplant or death. Light microscopy was used, with haematoxylin and eosin, reticulin and orcein stains. Tissue, plasma and water copper levels were measured by flame atomic absorption spectrometry.

RESULTS

All had micronodular cirrhosis and severe hepatocellular necrosis with Mallory bodies and copious-orcein positive material. Liver copper concentrations ranged from 1100-1310 micrograms/g dry weight. For two patients domestic water with high copper content had been used for the preparation of feeds. No environmental source of excess copper could be identified in the third case.

CONCLUSIONS

We suggest that the above condition, which is called Indian childhood cirrhosis in the Indian subcontinent and Copper Storage Disease elsewhere, would be better named 'Copper-Associated Liver Disease in Childhood', emphasising the need to consider this disorder in unexplained liver disease and to seek possible sources of excessive copper intake.

Atypical copper cirrhosis in Indian children

In addition to ten children with Wilson's disease and one with Indian childhood cirrhosis, nine Indian children, aged from 4 to 15 years, with cryptogenic cirrhosis had significant deposits of stainable copper in their hepatocytes. These nine children had normal or elevated serum caeruloplasmin levels, absence of Kayser-Fleischer rings and a history of sibling death owing to liver disease in four cases. Histologically, fatty change was absent from all the biopsies but Mallory's hyaline, pericellular fibrosis and ballooning of hepatocytes were present in some. Since these children did not conform to the accepted clinical or histological definitions of either Indian childhood cirrhosis or Wilson's disease, they were designated as having atypical copper cirrhosis. The relationship of this group of cases to other types of copper cirrhosis is unknown.

Synergistic liver toxicity of copper and retrorsine in the rat

To investigate the possible synergy between copper and retrorsine (a pyrrolizidine alkaloid) as a cause of Indian Childhood Cirrhosis, four groups of male Wistar rats were fed the following diets from weaning: A. Normal diet; B. Copper loaded (2 g CuSO4/kg diet); C. Retrorsine supplemented (Expt 1:25 mg/kg body weight/week by gavage, Expt 2:25 mg/kg food initially then 15 mg/kg food after 4 weeks); and D. Copper and retrorsine as above. Serial plasma samples were assayed for aminotransferases, albumin and bilirubin. Liver samples at biopsy and sacrifice provided samples for copper analysis and histology. Results showed that copper and retrorsine together significantly increased liver damage compared with feeding either alone as assessed by: 1. Increased mortality rate; 2. Decreased plasma albumin and increased plasma bilirubin (mainly conjugated) indicative of hepatocyte dysfunction; 3. Massive liver copper accumulation, and 4. Increased liver damage histologically. Thus retrorsine caused liver copper accumulation, and together copper and retrorsine led to severe hepatic dysfunction, characterised by hypoalbuminaemia and conjugated hyperbilirubinaemia. Plant alkaloids secreted in milk by grazing animals and copper from brass vessels may together produce Indian Childhood Cirrhosis.

Is non-Indian childhood cirrhosis caused by excess dietary copper?

Indian childhood cirrhosis is generally believed to be caused by toxic excesses of hepatic copper derived from milk boiled in copper vessels. Sporadic cases of a disorder indistinguishable from Indian childhood cirrhosis have appeared in other countries where the toxic hepatic copper has been thought to be derived from drinking water. In published reports of seven 2-year-old or younger infants with non-Indian childhood cirrhosis (five of whom died), the copper content of their drinking water--which the authors considered the essential, if not the sole, aetiological factor--ranged from 0.05 to 6.8 mg Cu/L. We identified three Massachusetts towns in which between 1969 and 1991 there were 64,124 child-years of exposure of children under the age of 6 years to drinking water that contained between 8.5 and 8.8 mg Cu/L. Data from the Massachusetts Department of Public Health showed that there were 135 deaths among these children, but no deaths from cirrhosis or any form of liver disease. These data, and evidence of a genetic aetiology in three of the seven infants reported previously, suggest that non-Indian childhood cirrhosis is an inherited disorder.