Concordance rates of Wilson's disease phenotype among siblings

Distal renal tubular acidosis as presenting manifestation of Wilson disease in a 11-year-old girl

A 11-year-old girl was referred to the pediatric nephrology services of our hospital for evaluation of vitamin-D-refractory rickets. She was born to second-degree consanguineous parents. On examination, she had wrist widening and bilateral genu varum. She had normal anion gap metabolic acidosis, hypokalemia, and hyperchloremia. The fractional excretion of bicarbonate was 3% and the urine anion gap was positive. She also had hypercalciuria, but no phosphaturia, glucosuria or aminoaciduria. In view of a family history of an elder sister having rigidity with cognitive and speech impairment, an ophthalmic evaluation by slit lamp examination was performed in the index case that revealed bilateral Kayser-Fleischer rings. Serum ceruloplasmin was low and 24-h urine copper was elevated in the index case. Whole exome sequencing unveiled a novel pathogenic variant in exon 2 of the ATP7B gene (chr13: c.470del; Depth: 142x) (homozygous) that resulted in a frameshift and premature truncation of the protein, 15 amino acids downstream to codon 157 (p. Cys157LeufsTer15; NM_000053.4) confirming Wilson disease. There were no mutations in the ATP6V0A4, ATP6V1B1, SLC4A1, FOXI1, WDR72 genes or other genes that are known to cause distal RTA. Therapy with D-penicillamine and zinc supplements was initiated. A low dose of 2.5 mEq/kg/day of potassium citrate supplementation normalized the serum bicarbonate levels. This case was notable for the absence of hepatic or neurological involvement at admission. Wilson disease is well known to cause proximal renal tubular acidosis and Fanconi syndrome, with relatively lesser involvement of the distal renal tubules in the literature. However, isolated distal renal tubular involvement as presenting manifestation of Wilson disease (without hepatic or neurological involvement) is rare and can lead to diagnostic confusion.

Role of gender and age in features of Wilson's disease

Background

Wilson's disease (WD) is a recessive genetic disorder characterized by copper metabolism dysfunction. It is difficult to obtain an accurate diagnosis due to its variable clinical presentation. This study aimed to describe the clinical characteristics and diagnostic particularities in a series of Chinese WD patients.

Methods

The medical records of 371 patients with WD retrieved from January 2005 to December 2020 were retrospectively reviewed.

Results

The incidence of WD has a male predominance in the adult population. However, the difference in sex distribution is not significant in the pediatric population. Females have an earlier symptom onset than males. The most common initial symptoms were neuropsychiatric manifestations both in the pediatric population (49.7%) and adult population (69.8%), and there was a male predominance (61.8%). Eighty-two percent of patients presented with more than two neurologic symptoms. Fifty-two (14%) patients presented with psychiatric symptoms. The most common WD phenotype was the neuropsychiatric form (48%). The age of onset occurred earlier in patients with the hepatic phenotype than in those with the neuropsychiatric phenotype. Moreover, there was a significant difference in sex distribution regarding phenotype. Females presented with a hepatic phenotype more often than males, and the neuropsychiatric phenotype occurred more frequently in males with an older onset age. Further study showed that the age at onset was a deciding factor for predicting the neuropsychiatric phenotype among the hepatic phenotype. However, sex did not correlate with the phenotype.

Conclusion

Males seem to have a higher disease susceptibility, with symptom onset later than females. Males frequently present with a neuropsychiatric phenotype, while females present with a hepatic phenotype. Age at onset was a deciding factor for predicting the WD phenotype. Further studies focusing on the effect of estrogens on the pathology of WD are suggested.

Investigation and management of Wilson's disease: a practical guide from the British Association for the Study of the Liver

Wilson's disease is an autosomal-recessive disorder of copper metabolism with hepatic, neurological, psychiatric, ophthalmological, haematological, renal, and rheumatological manifestations. Making a diagnosis can be challenging given that no single test can confirm or exclude the disease, and diagnostic delays are common. Treatment protocols vary and adverse effects, including paradoxical neurological worsening, can occur. In this Review, we provide a practical guide to the diagnosis of Wilson's disease. We include recommendations on indications for testing, how to interpret results, and when additional investigations are required. We also cover treatment initiation, ideally under the guidance of a specialist centre for Wilson's disease, and the principles behind long-term management. This guidance was developed by a multidisciplinary group of Wilson's disease experts formed through the British Association for the Study of the Liver. The guidance has been endorsed by the British Society of Gastroenterology and approved by the Association of British Neurologists.

Copper-Induced Epigenetic Changes Shape the Clinical Phenotype in Wilson's Disease

Wilson's disease is a congenital disorder of copper metabolism whose pathogenesis remains, at least in part, unknown. Subjects carrying the same genotype may show completely different phenotypes, differing for the age at illness onset or for the hepatic, neurologic or psychiatric clinical presentation. The inability to find a unequivocal correlation between the type of mutation in the ATPase copper transporting beta (ATP7B) gene and the phenotypic manifestation, has encouraged many authors to look for epigenetic factors interacting with the genetic changes. Here, the evidences regarding the ability of copper overload to change the global DNA methylation status are discussed.

Genotype-phenotype variable correlation in Wilson disease: clinical history of two sisters with the similar genotype

Background

Wilson disease (WD) is an Autosomal-Recessive disorder due to mutations of ATP7B gene on chromosome 13q14.3. Inadequate protein function leads to low ceruloplasmin blood levels and copper accumulation in liver, basal ganglia and chornea. Main clinical manifestations are hypertransaminasemia, tremors, dysarthria, dystonia and psychiatric symptoms. The phenotypic variability in WD is considerable and its onset can be heterogeneous: the most common type in childhood is the hepatic involvement, followed by the neurological one or others. The presence of a genotype-phenotype correlation has not yet been fully demonstrated. The phenotypic variability may be explained by the intervention of other modifier genes regulating copper metabolism in the presence of mutations ATP7B.

Case presentation

A streaking phenotypic variability was observed in two Sicilian sisters carrying the same genotype for ATB7B gene [c.3207C > A / c.3904-2A > G]. Although both started to present signs at age 10 years, onset was characterized by neurological signs in the first (tremors, motor incoordination, language and cognitive impairment), while liver involvement has been the only sign in the other. They started the same chelation therapy. After a 20-year follow-up the former is severely affected (MRI evidence of basal ganglia copper deposits and hyperchogenic liver, thrombocytopenia), while the latter presents only a moderate liver enlargement. In literature, the splice mutation c.3904-2A > G is also reported in Egypt population, associated with acute liver failure or chronic hepatic disease, and it could be typical of Mediterranean area, not being reported in other geographical zones.

Conclusion

Based on our clinical experience in Eastern Sicily, there is a considerable phenotypic variability in WD, even in the presence of an identical genotype. The mutation c.3904-2A > G could be associated with this phenotypic variability in Mediterranean population, but further studies should be conducted. This condition could be explained by the intervention of modifier genes regulating copper metabolism in the presence of defective ATP7B protein function. Further investigations on their role by Next Generation Sequencing or Whole Exome Analysis might have a profound impact on patients’ management and in particular on therapy.

Clinical presentations of Wilson disease

The main presenting features of Wilson disease, many of which mimic common hepatic and neurologic disorders, are discussed. There is a need for specialists in these and related fields to be aware of hints from within and, more importantly, outside their area of expertise that should alert them to consider the diagnosis. Delayed diagnosis and treatment are potentially damaging for the patient. The importance of recognising and promptly investigating Wilson disease at the initial presentation should be understood by all those who assess patients with hepatic or neurologic disorders and/or train others in their specialty.

Genetics and epigenetic factors of Wilson disease

Wilson disease (WD) is a complex condition due to copper accumulation mainly in the liver and brain. The genetic base of WD is represented by pathogenic mutations of the copper-transporting gene ATP7B with consequent lack of copper excretion through the biliary tract. ATP7B is the only gene so far identified and known to be responsible for the development of the disease. Our understanding of the disease has been evolving as functional studies have associated specific disease-causing mutations with specific copper-transporter impairments. The most frequent variant in patients of European descent is the H1069Q missense mutation and it has been associated with protein misfolding, aberrant phosphorylation of the P-domain, and altered ATP binding orientation and affinity. Conversely, there is much less understanding of the relation between the genotype and the clinical manifestations of WD. WD is characterized by a highly varied and unpredictable presentation with different combined hepatic, neurological, and psychiatric symptoms. Several studies have attempted to correlate genotype and phenotype but the most recent evidences on larger populations failed to identify a relation between genotype and clinical presentations. Given that so far also modifier genes have not shown convincing association with WD, there is growing interest to identify epigenetic mechanisms of gene expression regulation as underlying the onset and progression of WD phenotype. Evidence from animal models indicated changes in methionine metabolism regulation with possible effects on DNA methylation. Mouse models of WD have indicated transcript level changes of genes related to DNA methylation in fetal and adult livers. And finally, evidence is accumulating regarding DNA methylation changes in patients with WD. It is unexplored how ATP7B genetic mutations combine with epigenetic changes to affect the phenotype. In conclusion, WD is a genetic disease with a complex regulation of its phenotype that includes molecular genetics and epigenetic mechanisms.

Whole-exome sequencing identifies novel pathogenic variants across the ATP7B gene and some modifiers of Wilson's disease phenotype

BACKGROUND & AIMS

Wilson's disease (WD) is an autosomal recessive disorder associated with disease-causing alterations across the ATP7B gene, with highly variable symptoms and age of onset. We aimed to assess whether the clinical variability of WD relates to modifier genes.

METHODS

A total of 248 WD patients were included, of whom 148 were diagnosed after age of 17. Human exome libraries were constructed using AmpliSeq technology and sequenced using the IonProton platform.

RESULTS

ATP7B p.His1069Gln mutation was present in 215 patients, with 112 homozygotes and 103 heterozygotes. Three other mutations: p.Gln1351Ter, p.Trp779Ter and c.3402delC were identified in >10 patients. Among patients, 117 had a homozygous mutation, 101 were compound heterozygotes, 27 had one heterozygous mutation, and 3 other patients had no identifiable pathogenic variant of ATP7B. Sixteen mutations were novel, found as part of a compound mutation or as a sole, homozygous mutation. For disease phenotype prediction, age at diagnosis was a deciding factor, while frameshift allelic variants of ATP7B and being male increased the odds of developing a neurological phenotype. Rare allelic variants in ESD and INO80 increased and decreased chances for the neurological phenotype, respectively, while rare variants in APOE and MBD6 decreased the chances of WD early manifestation. Compound mutations contributed to earlier age of onset.

CONCLUSIONS

In a Polish population, genetic screening for WD may help genotype for four variants (p.His1069Gln, p.Gln1351Ter, p.Trp779Ter and c.3402delC), with direct sequencing of all ATP7B amplicons as a second diagnostic step. We also identified some allelic variants that may modify a WD phenotype.

Epidemiology and introduction to the clinical presentation of Wilson disease

Our understanding of the epidemiology of Wilson disease has steadily grown since Sternlieb and Scheinberg's first prevalence estimate of 5 per million individuals in 1968. Increasingly sophisticated genetic techniques have led to revised genetic prevalence estimates of 142 per million. Various population isolates exist where the prevalence of Wilson disease is higher still, the highest being 885 per million from within the mountainous region of Rucar in Romania. In Sardinia, where the prevalence of Wilson disease has been calculated at 370 per million births, six mutations account for around 85% of Wilson disease chromosomes identified. Significant variation in the patterns of presentation may however exist, even between individuals carrying the same mutations. At either extremes of presentation are an 8-month-old infant with abnormal liver function tests and individuals diagnosed in their eighth decade of life. Three main patterns of presentation have been recognized - hepatic, neurologic, and psychiatric - prompting their presentation to a diverse range of specialists. Deviations in the family history from the anticipated autosomal-recessive mode of inheritance, with apparent "pseudodominance" and mechanisms of inheritance that include uniparental isodisomy (the inheritance of both chromosomal copies from a single parent), may all further cloud the diagnosis. It can therefore take the efforts of an astute clinician with a high clinical index of suspicion to clinch the diagnosis of this eminently treatable condition.

Wilson disease: At the crossroads between genetics and epigenetics-A review of the evidence

Environmental factors, including diet, exercise, stress, and toxins, profoundly impact disease phenotypes. This review examines how Wilson disease (WD), an autosomal recessive genetic disorder, is influenced by genetic and environmental inputs. WD is caused by mutations in the copper-transporter gene ATP7B, leading to the accumulation of copper in the liver and brain, resulting in hepatic, neurological, and psychiatric symptoms. These symptoms range in severity and can first appear anytime between early childhood and old age. Over 300 disease-causing mutations in ATP7B have been identified, but attempts to link genotype to the phenotypic presentation have yielded little insight, prompting investigators to identify alternative mechanisms, such as epigenetics, to explain the highly varied clinical presentation. Further, WD is accompanied by structural and functional abnormalities in mitochondria, potentially altering the production of metabolites that are required for epigenetic regulation of gene expression. Notably, environmental exposure affects the regulation of gene expression and mitochondrial function. We present the "multi-hit" hypothesis of WD progression, which posits that the initial hit is an environmental factor that affects fetal gene expression and epigenetic mechanisms and subsequent "hits" are environmental exposures that occur in the offspring after birth. These environmental hits and subsequent changes in epigenetic regulation may impact copper accumulation and ultimately WD phenotype. Lifestyle changes, including diet, increased physical activity, stress reduction, and toxin avoidance, might influence the presentation and course of WD, and therefore may serve as potential adjunctive or replacement therapies.

Phenotypes and Chronic Organ Damage May Be Different among Siblings with Wilson's Disease

Background and Aims: Cloning of ATP7B provided evidence that Wilson's disease is a hepatic copper toxicosis with a variety of extrahepatic complications. Affected siblings with the same genetic background and exposure to similar environmental factors may be a good model for the study of genotype-phenotype correlation. Methods: Twenty-three affected siblings in 11 families were selected from a database. The first phenotypes were determined according to the international proposal. The final types of chronic organ damage were re-evaluated for life-long management. Results: Phenotypes were identical in 5 of the families and different in 6 of the families. The acute hepatic phenotype H1 was found in 3 younger siblings and 1 older sibling. All survived an acute episode of hemolysis with underlying chronic liver disease. One also presented complication with neurological disease. The neurological phenotype N1 with neuropsychiatric symptoms and hepatic disease was found in 2 aged siblings of 1 family, in an older sibling in 3 families and in the oldest sibling in 1 family. Phenotypes in siblings were mainly split by either H1 occurring in random order or age-dependent N1. Types of chronic organ damage were identical in 8 of the families and different in 3 of the families. The same combination of chronic liver disease was found in 6 families and chronic liver disease complicated with neurological disease in 2 families. Split organ damage in siblings was found when an older sibling was complicated by neurological disease. There was no reverse combination of a younger sibling being complicated by neurological disease in any of the families. Conclusion: Phenotype combinations of siblings were mainly modified by externally-induced hemolytic episodes, while chronic organ damage in siblings was split by age-dependent neurological complications.

The genetics of Wilson disease

Wilson disease (WD) is an autosomal-recessive disorder of hepatocellular copper deposition caused by pathogenic variants in the copper-transporting gene, ATP7B. Early detection and treatment are critical to prevent lifelong neuropsychiatric, hepatic, and systemic disabilities. Due to the marked heterogeneity in age of onset and clinical presentation, the diagnosis of Wilson disease remains challenging to physicians today. Direct sequencing of the ATP7B gene is the most sensitive and widely used confirmatory testing method, and concurrent biochemical testing improves diagnostic accuracy. More than 600 pathogenic variants in ATP7B have been identified, with single-nucleotide missense and nonsense mutations being the most common, followed by insertions/deletions, and, rarely, splice site mutations. The prevalence of Wilson disease varies by geographic region, with higher frequency of certain mutations occurring in specific ethnic groups. Wilson disease has poor genotype-phenotype correlation, although a few possible modifiers have been proposed. Improving molecular genetic studies continue to advance our understanding of the pathogenesis, diagnosis, and screening for Wilson disease.

Update on the clinical management of Wilson's disease

Wilson's disease (WD), albeit relatively rare, is an important genetic metabolic disease because of highly effective therapies that can be lifesaving. It is a great imitator and requires a high index of suspicion for correct and timely diagnosis. Neurologic, psychiatric and hepatologic problems in WD are very nonspecific, and we discuss the most common clinical phenotypes. The diagnosis remains laboratory based, and here we review the most important challenges and pitfalls in laboratory evaluation of WD, including the emerging role of genetic testing in WD diagnosis. WD is a monogenic disorder but has very high allelic heterogeneity with >500 disease-causing mutations identified, and new insights into phenotype-genotype correlations are also reviewed. The gold standard of therapy is chelation of excessive copper, but many unmet needs exist because of possible clinical deterioration in treated patients and potential adverse effects associated with currently available chelating medications. We also review the most promising novel therapeutic approaches, including chelators targeting specific cell types, cell transplantation and gene therapy.

Phenotype-genotype correlation in Wilson disease in a large Lebanese family: association of c.2299insC with hepatic and of p. Ala1003Thr with neurologic phenotype

Genotype phenotype correlations in Wilson disease (WD) are best established in homozygous patients or in compound heterozygous patients carrying the same set of mutations. We determined the clinical phenotype of patients with WD carrying the c.2298_2299insC in Exon 8 (c.2299insC) or the p. Ala1003Thr missense substitution in Exon 13 mutations in the homozygous or compound heterozygous state. We investigated 76 members of a single large Lebanese family. Their genotypes were determined, and clinical assessments were carried out for affected subjects. We also performed a literature search retrieving the phenotypes of patients carrying the same mutations of our patients in the homozygous or compound heterozygous state. There were 7 consanguineous marriages in this family and the prevalence of WD was 8.9% and of carriers of ATP7B mutation 44.7%. WD was confirmed in 9 out of 76 subjects. All 9 had the c.2299insC mutation, 5 homozygous and 4-compound heterozygous with p. Ala1003Thr. Six of our patients had hepatic, 2 had neurologic and 1 had asymptomatic phenotype. Based on our data and a literature review, clear phenotypes were reported for 38 patients worldwide carrying the c.2299insC mutation. About 53% of those have hepatic and 29% have neurologic phenotype. Furthermore, there were 10 compound heterozygous patients carrying the p. Ala1003Thr mutation. Among those, 80% having c.2299insC as the second mutation had hepatic phenotype, and all others had neurologic phenotype. We hereby report an association between the c.2299insC mutation and hepatic phenotype and between the p. Ala1003Thr mutation and neurologic phenotype.

Genotype-phenotype correlations in a mountain population community with high prevalence of Wilson's disease: genetic and clinical homogeneity

Wilson’s disease is an autosomal recessive disorder caused by more than 500 mutations in ATP7B gene presenting considerably clinical manifestations heterogeneity even in patients with a particular mutation. Previous findings suggested a potential role of additional genetic modifiers and environment factors on phenotypic expression among the affected patients. We conducted clinical and genetic investigations to perform genotype-phenotype correlation in two large families living in a socio-culturally isolated community with the highest prevalence of Wilson’s disease ever reported of 1∶1130. Sequencing of ATP7B gene in seven affected individuals and 43 family members identified a common compound heterozygous genotype, H1069Q/M769H-fs, in five symptomatic and two asymptomatic patients and detected the presence of two out of seven identified single nucleotide polymorphisms in all affected patients. Symptomatic patients had similar clinical phenotype and age at onset (18±1 years) showing dysarthria and dysphagia as common clinical features at the time of diagnosis. Moreover, all symptomatic patients presented Kayser-Fleischer rings and lack of dystonia accompanied by unfavourable clinical outcomes. Our findings add value for understanding of genotype-phenotype correlations in Wilson’s disease based on a multifamily study in an isolated population with high extent of genetic and environmental homogeneity as opposed to majority of reports. We observed an equal influence of presumed other genetic modifiers and environmental factors on clinical presentation and age at onset of Wilson’s disease in patients with a particular genotype. These data provide valuable inferences that could be applied for predicting clinical management in asymptomatic patients in such communities.

Phenotype-genotype correlations in patients with Wilson's disease

There is considerable phenotypic variation in Wilson's disease (WD). Some patients present with hepatic disease during the first decade of life and some with neurological degeneration in adolescence or adult life, with or without overt liver disease. Although the absence of neurologic disease in patients with liver disease in childhood or adolescence can be explained by the limited time exposure of the central nervous system to copper toxicity, it is surprising that late-onset neurologic WD can occur without any evidence of liver involvement. This huge variability in the clinical presentation of WD in general reflects our limited knowledge on the natural history of WD. Genetic association studies require the phenotype to be defined as accurately as possible.