ATP7B variant penetrance explains differences between genetic and clinical prevalence estimates for Wilson disease

Low penetrance of frequent ATP7B mutations explains the low prevalence of Wilson disease. Lessons from real-life registries

BACKGROUND & AIMS

Wilson disease (WD) is a copper metabolism disorder caused by mutations in ATP7B gene, with significant clinical variability. Several studies have analyzed the prevalence and penetrance of mutations. We evaluated both characteristics for our more frequent mutations.

METHODS

Evaluation of 260 patients from the National Registry: clinical, analytical and genetic data. Estimation of homozygotes and total cases according to Hardy-Weinberg equilibrium and comparison with Registry records.

RESULTS

The estimated number of homozygotes were higher than registered: p.Met645Arg (1949/6), p.His1069Gln (20/8), p.Leu708Pro (63/24) and p.Gly869Arg (147/0). p.Met645Arg homozygotes presented less cirrhosis at diagnosis, extrahepatic disease and Kayser-Fleischer ring (KFR) and more presymptomatic cases and diagnosis after 40 years of age than p.Leu708Pro and p.His1069Gln homozygotes. p.Met645Arg homozygotes presented more late diagnosis than p.Met645Arg compound heterozygotes. Compound heterozygotes carrying p.Met645Arg or p.Gly869Arg showed less cirrhosis at diagnosis, KFR and neurological symptoms and more hepatic and presymptomatic cases, despite clearly low ceruloplasmin levels. The estimated prevalence was 1:3.785, predicting more than 10.500 patients.

CONCLUSIONS

The widespread mutations p.Met645Arg and p.Gly869Arg show low penetrance. WD might be underdiagnosed in Spain due to less severe phenotype of the most frequent mutations, a crucial fact to avoid misdiagnosis and to offer early therapy.

Epidemiology of Wilson disease in Germany - real-world insights from a claims data study

BACKGROUND

Wilson disease (WD) is a rare disorder of copper metabolism, causing copper accumulation mainly in the liver and the brain. The prevalence of WD was previously estimated around 20 to 33.3 patients per million for the United States, Europe, and Asia, but data on the prevalence of WD in Germany are limited.

OBJECTIVES

To describe patient characteristics and to assess prevalence of WD in Germany using a representative claims database.

METHODS

WD patients were identified in the WIG2 (Wissenschaftliches Institut für Gesundheitsökonomie und Gesundheitssystemforschung; Scientific Institute for Health Economics and Health Systems Research) benchmark database of 4.5 million insured Germans by combining ICD-10-coding with WD-specific lab tests and treatments. The study period ranged from 2013 to 2016 for assessing patient characteristics, and to 2018 for prevalence, respectively.

RESULTS

Seventy unique patients were identified. Most patients (86%) were between 18 and 64 years of age and more often male (60%) than female. Two patients (3%) younger than 18 years were included, as well as 8 patients (11%) older than 64 years. Most common WD subtypes were hepatic (57%), psychiatric (49%), and neurologic (44%). Average prevalence was 20.3 patients per million (range: 17.8-24.4), with similar results for two-year prevalence. Generally, prevalence increased steadily over the study period. Observed mortality was low, with only one death during the study period.

CONCLUSIONS

This study adds valuable real-world data on the prevalence and patient characteristics of WD in Germany. Generally, our findings align with other reports and contribute to the global understanding of WD epidemiology. Still, regional and temporal trends remain to be investigated more thoroughly to further the understanding of the natural history and epidemiology of this rare disease.

Investigating common mutations in ATP7B gene and the prevalence of Wilson's disease in the Thai population using population-based genome-wide datasets

Wilson's disease (WD) is a rare metabolic disorder caused by variations in the ATP7B gene. It usually manifests hepatic, neurologic, and psychiatric symptoms due to excessive copper accumulation. The prevalence of WD and its common variants differ across populations. This study aimed to examine these aspects of WD within the Thai population, where information has been limited. We reviewed ClinVar and the Wilson Disease Mutation Database, organizing variants classified as pathogenic or likely pathogenic in one or both databases as "relaxed" and "strict" lists. Allele frequencies were estimated from genotyping array data (Asian Screening Array: ASA; Illumina Corp, CA) of 6291 Thai subjects, which also underwent genotype imputation. The prevalence of WD in the Thai population was estimated assuming Hardy-Weinberg Equilibrium. The strict list yielded a prevalence of 1/24,128 (carrier frequency=1/78), while the relaxed list yielded a prevalence of 1/9971 (carrier frequency=1/50). The most common WD variants in Thai subjects were c.2333 G > T, c.3443 T > C, and c.813 C > A from the strict list, and c.3316 G > A and c.2605 G > A from the relaxed list. The ASA chip covered approximately 59 and 24% of WD variants from the strict and relaxed lists, respectively. Based on the estimated prevalence, a carrier screening program for WD is not currently required in Thailand. However, as genotyping services become more affordable and accessible, such a program would facilitate early identification, treatment, and prevention of WD.

Rare liver diseases in Egypt: Clinical and epidemiological characterization

Illnesses that afflict a tiny number of individuals are referred to as rare diseases (RDs), sometimes called orphan diseases. The local healthcare systems are constantly under financial, psychological, and medical strain due to low incidence rates, unusual presentations, flawed diagnostic standards, and a lack of treatment alternatives for these RDs. The effective management of the once widely spread viral hepatitis B and C has altered the spectrum of liver diseases in Egypt during the last several years. The detection of uncommon disorders such as autoimmune, cholestatic, and hereditary liver diseases has also been made easier by the increasing knowledge and greater accessibility of specific laboratory testing. Finally, despite Egypt's large population, there are more uncommon liver disorders than previously thought. This review article discusses the clinical and epidemiological characteristics of a few uncommon liver disorders and the information currently accessible concerning these illnesses in Egypt.

Late-onset Wilson Disease in a Patient Followed-up for Nonalcoholic Fatty Liver Disease

A 73-year-old woman was referred to our hospital for persistent liver dysfunction. When the patient was 45 years old, her youngest sister had been diagnosed with Wilson disease (WD). The patient therefore underwent several family screening tests, all of which were unremarkable. She had an annual medical checkup and was diagnosed with liver dysfunction and fatty liver at 68 years old. A liver biopsy and genetic testing were performed, and she was diagnosed with WD; chelation therapy was then initiated. In patients with hepatic disorders and a family history of WD, multiple medical examinations should be conducted, as the development of WD is possible regardless of age.

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.

Wilson disease: a summary of the updated AASLD Practice Guidance

Wilson disease (WD) is caused by autosomal variants affecting the ATP7B gene on chromosome 13, resulting in alterations in physiological copper homeostasis and copper accumulation. Excess copper clinically manifests in many organs, most often in the central nervous system and liver, ultimately causing cirrhosis and death. Often considered a pediatric or young adult disease, WD actually affects patients of all ages, and aging patients need to be regularly managed with long-term follow-up. Despite over a century of advances in diagnosis and treatment, WD is still associated with diagnostic challenges and considerable disability and death, in part due to delays in diagnosis and limitations in treatment. Standard-of-care treatments are considered generally effective when the diagnosis is timely but are also limited by efficacy, safety concerns, multiple daily dosing, and adherence. This expert perspective review seeks to facilitate improvements in the awareness, understanding, diagnosis, and management of WD. The objectives are to provide a full overview of WD and streamline updated diagnosis and treatment guidance, as recently published by the American Association for the Study of Liver Diseases, in a practical way for clinical use.

Medical care of patients with Wilson disease in Germany: a multidisciplinary survey among university centers

BACKGROUND

Wilson disease (WD) is a rare, hereditary disorder of copper metabolism. Due to its variable symptoms and manifestations, diagnosis remains challenging. Affected patients must obtain lifelong medical treatment, as the disease is fatal if untreated. Patients require continuous monitoring, but little is known about the care of these patients in Germany. Therefore, we analyzed the medical care of WD patients at German university centers. We sent a questionnaire containing 20 questions to a total of 108 departments of pediatrics, neurology and gastroenterology in 36 university hospitals. Our questions referred to the characteristics of WD patients at the different sites and internal procedures regarding diagnosis, therapy and follow-up. A descriptive statistical analysis was performed.

RESULTS

Sixty-three departments (58%) returned our questionnaire. In total, approximately one-third of the estimated WD patients in Germany are seen annually in the outpatient clinics of these departments (approx. 950 patients). There are only a few departments which treat patients in a multidisciplinary setting (12%). Our survey revealed that for diagnosis, 51% of all departments used an algorithm based on the Leipzig score as recommended by international guidelines. Most departments apply essential parameters recommended by WD guidelines. Routine monitoring is performed at least biannually by 84% of the departments, and standard investigations for monitoring are regularly applied. A routine family screening is performed by 84% of all departments. A reduction in medical therapy during pregnancy is recommended by 46% of the departments. Only 14% suggested that WD patients should not breastfeed. Liver transplantation (LT) due to WD is a rare but repeatedly occurring event. Most departments of gastroenterology (72%) reported at least one patient with LT within the last decade.

CONCLUSIONS

Medical care of WD patients at German university centers follows the recommendations set forth by international guidelines, but only a few centers treat significant numbers of patients. The surveillance of patients does not follow specified standards, but most departments adhere to the accepted guidelines. The formation of central units and networks in a multidisciplinary setting should be evaluated to improve the care of WD patients.

Functional characterization of novel or yet uncharacterized ATP7B missense variants detected in patients with clinical Wilson's disease

Wilson's disease (WD, MIM#277900) is an autosomal recessive disorder resulting in copper excess caused by biallelic variants in the ATP7B gene (MIM#606882) encoding a copper transporting P-type ATPase. ATP7B variants of unknown significance (VUS) are detected frequently, sometimes impeding a clear diagnosis. Functional analyses can help to classify these variants as benign or pathogenic. Additionally, variants already classified as (likely) pathogenic benefit from functional analyses to understand their pathomechanism, thus contribute to the development of personalized treatment approaches in the future. We described clinical features of six WD patients and functionally characterized five ATP7B missense variants (two VUS, three yet uncharacterized likely pathogenic variants), detected in these patients. We determined the protein level, copper export capacity, and cellular localization in an in vitro model and potential structural consequences using an ATP7B protein model based on AlphaFold. Our analyses give insight into the pathomechanism and allowed reclassification for the two VUS to likely pathogenic and for two of the three likely pathogenic variants to pathogenic.

A Systematic Review and Meta-Analysis of the R778L Mutation in ATP7B With Wilson Disease in China

BACKGROUND

Wilson disease (WD) is a hereditary disorder of copper metabolism, caused by mutations in the ATP7B gene. There are more than 1000 pathogenic variants identified in ATP7B. R778L is the most common ATP7B mutation in China.

METHODS

To estimate whether R778L is associated with the onset age of WD and other clinical variables. Genotyping results of ATP7B gene were collected in our 22 patients with WD. We then conducted a systematic review and meta-analysis in databases, using the keywords Wilson disease and R778L mutation.

RESULTS

After the screening, a total of 23 studies were included, including 3007 patients with WD. Patients with R778L mutation presented at an earlier age (standardized mean difference [SMD] = -0.18 [95% confidence interval, -0.28 to 0.08], P = 0.0004) and had lower ceruloplasmin concentration (SMD = -0.21 [95% confidence interval, -0.40 to -0.02], P = 0.03) than the patients without the R778L mutation. However, sex (odds ratio [OR] = 1.07 [95% confidence interval, 0.89 to 1.29], P = 0.32) and first presentation were not associated with R778L mutation in WD (hepatic: OR = 1.37 [95% confidence interval, 0.87 to 2.16, P = 0.17; neurological: OR = 0.79 [95% confidence interval, 0.48 to 1.30, P = 0.35; mix: OR = 1.04 [95% confidence interval, 0.42 to 2.53, P = 0.87; asymptomatic/others: OR = 1.98 [95% confidence interval, 0.49 to 7.96, P = 0.34).

CONCLUSIONS

Our results indicated that the R778L mutation is associated with an earlier presentation and lower ceruloplasmin concentration in China.

Clinical spectrum and genotype-phenotype associations in Finnish patients with Wilson's disease

Genotype-phenotype correlation data covering all ages of Wilson's disease onset in Caucasian patients are limited. We therefore analyzed genotype-phenotype correlations in a retrospective cohort of Finnish patients. Six homozygous (HoZ) and 11 compound heterozygous (CoHZ) patients were included. There were no differences in the presence/absence of hepatic, neurological, psychiatric or any symptoms at diagnosis (p > 0.30 for all) between HoZ and CoHZ patients, but HoZ patients had an earlier age of diagnosis (median 6.7 versus 34.5; p = 0.003). Severe liver affliction was almost exclusively associated with the p.H1069Q variant. Patients with p.H1069Q had a later mean age of diagnosis (30.2 ± 11.6 vs. 8.7 ± 4.9 years; p < 0.001) compared to those without. There were no differences in the presence/absence of hepatic, neurological, psychiatric or any symptoms at diagnosis between p.H1069Q-positive and p.H1069Q-negative patients (p > 0.54 for all). These results suggest that population-specific factors may partly explain the high clinical variability of Wilson's disease.

Wilson's disease: best practice

Wilson's disease is an autosomal recessive disorder arising from pathogenic variants in the Atp7b gene on chromosome 13. The defective translated ATPase copper (Cu) transport protein produced leads to Cu accumulation, initially affecting the liver but eventually affecting other cells. It is just over 20 years since the last Best Practice on this topic in this journal. This review is an update on this, covering new disease biomarkers, pathogenesis, assumptions around clinical features and developments in therapy.

Antioxidant Capacity Is Decreased in Wilson's Disease and Correlates to Liver Function

The metabolic disorder Wilson's disease (WD) is caused by copper accumulation in the tissues due to a biallelic pathogenic mutation of the gene ATP7B, encoding intracellular copper transporter ATPase-7B. As copper is a redox active metal; aberrations in its homeostasis may create favourable conditions for superoxide-yielding redox cycling and oxidative damage to the cells. We tried to characterise antioxidant defence in WD patients and to evaluate whether it is related to liver function. The blood glutathione concentration, the activity of manganese-SOD (MnSOD), catalase (Cat), glutathione peroxidase, and glutathione S-transferase glutathione (GST), and serum antioxidant potential (AOP-450) were measured in WD treatment-naive patients and healthy controls and correlated with clinical data. The blood glutathione concentration, the activity of MnSOD, Cat, glutathione peroxidase, and GST and AOP-450 are significantly decreased in WD patients. There was a positive correlation of AOP-450 with AST. Moreover, the Cat and GST activity as well as AOP-450 strongly correlated with parameters of synthetic liver function. MnSOD activity correlated positively with ALT and AST.The blood glutathione concentration, the activity of MnSOD, Cat, glutathione peroxidase, and GST and AOP-450 are significantly decreased in WD patients. There was a positive correlation of AOP-450 with AST. Moreover, the Cat and GST activity as well as AOP-450 strongly correlated with parameters of synthetic liver function. MnSOD activity correlated positively with ALT and AST. Liver injury in course of WD is linked with decreased antioxidant capacity.

Wilson’s Disease—Genetic Puzzles with Diagnostic Implications

(1) Introduction: Wilson’s disease (WND) is an autosomal recessive disorder of copper metabolism. The WND gene is ATP7B, located on chromosome 13. WND is characterized by high clinical variability, which causes diagnostic difficulties. (2) Methods: The PubMed, Science Direct, and Wiley Online Library medical databases were reviewed using the following phrases: “Wilson’s disease”, “ATP7B genotype”, “genotype-phenotype”, “epigenetics”, “genetic modifiers”, and their combinations. Publications presenting the results of experimental and clinical studies, as well as review papers, were selected, which concerned: (i) the diversity of genetic strategies and tests used in WND diagnosis; (ii) the difficulties of genetic diagnosis, including uncertainty as to the pathogenicity of variants; (iii) genetic counseling; (iv) phenotypic effects of ATP7B variants in patients with WND and in heterozygous carriers (HzcWND); (v) genetic and epigenetics factors modifying the clinical picture of the disease. (3) Results and conclusions: The genetic diagnosis of WND is carried out using a variety of strategies and tests. Due to the large number of known variants in the ATP7B gene (>900), the usefulness of genetic tests in routine diagnostics is still relatively small and even analyses performed using the most advanced technologies, including next-generation sequencing, require additional tests, including biochemical evidence of abnormal copper metabolism, to confirm the diagnosis of WND. Pseudodominant inheritance, the presence of three various pathogenic variants in the same patient, genotypes indicating the possibility of segmental uniparental disomy, have been reported. Genotype–phenotype relationships in WND are complex. The ATP7B genotype, to some extent, determines the clinical picture of the disease, but other genetic and epigenetic modifiers are also relevant.

A Century of Progress on Wilson Disease and the Enduring Challenges of Genetics, Diagnosis, and Treatment

Wilson disease (WD) is a rare, inherited metabolic disorder manifested with varying clinical presentations including hepatic, neurological, psychiatric, and ophthalmological features, often in combination. Causative mutations in the ATP7B gene result in copper accumulation in hepatocytes and/or neurons, but clinical diagnosis remains challenging. Diagnosis is complicated by mild, non-specific presentations, mutations exerting no clear effect on protein function, and inconclusive laboratory tests, particularly regarding serum ceruloplasmin levels. As early diagnosis and effective treatment are crucial to prevent progressive damage, we report here on the establishment of a global collaboration of researchers, clinicians, and patient advocacy groups to identify and address the outstanding challenges posed by WD.

Clinical and genetic characterization of pediatric patients with Wilson's disease from Yunnan province where ethnic minorities gather

Background: Wilson's disease (WD) is an autosomal recessive disease that is caused by mutations in the ATP7B (a copper-transporting P-type ATPase) gene. The disease has a low prevalence and is characterized by a copper metabolism disorder. However, various characteristics of the disease are determined by race and geographic region. We aimed to discover novel ATP7B mutations in pediatric patients with WD from Yunnan province, where there is a high proportion of ethnic minorities. We also performed a comprehensive analysis of ATP7B mutations in the different ethnic groups found in Southwest China. Methods: We recruited 45 patients who had been clinically diagnosed with WD, from 44 unrelated families. Routine clinical examinations and laboratory evaluations were performed and details of age, gender, ethnic group and symptoms at onset were collected. Direct sequencing of the ATP7B gene was performed in 39 of the 45 patients and their families. Results: In this study, participants came from seven different ethnic groups in China: Han, Bai, Dai, Zhuang, Yi, Hui and Jingpo. Three out of ten patients from ethnic minorities presented with elevated transaminases, when compared to the majority of the Han patients. Forty distinct mutations (28 missense, six splicing, three non-sense, two frameshift and one mutation of uncertain significance) were identified in the 39 patients with WD. Four of the mutations were novel and the most frequent mutation was c.2333G > T (p.R778L, allelic frequency: 15.38%). Using the phenotype-genotype correlation analysis, patients from ethnic minorities were shown to be more likely to have homozygous mutations (p = 0.035) than Han patients. The patients who carried the c.2310C > G mutation had lower serum ceruloplasmin levels (p = 0.012). In patients with heterozygous mutations, c.3809A > G was significantly associated with ethnic minorities (p = 0.042). The frequency of a protein-truncating variant (PTV) in Han patients was 34.38% (11/32), while we did not find PTV in patients from ethnic minorities. Conclusion: This study revealed genetic defects in 39 pediatric patients with WD from Yunnan province. Four novel mutations were identified and have enriched the WD database. We characterized the genotypes and phenotypes in different minorities, which will enhance the current knowledge on the population genetics of WD in China.

Re-evaluation of the existing health-based guidance values for copper and exposure assessment from all sources

Copper is an essential micronutrient and also a regulated product used in organic and in conventional farming pest management. Both deficiency and excessive exposure to copper can have adverse health effects. In this Scientific Opinion, the EFSA 2021 harmonised approach for establishing health-based guidance values (HBGVs) for substances that are regulated products and also nutrients was used to resolve the divergent existing HBGVs for copper. The tightly regulated homeostasis prevents toxicity manifestation in the short term, but the development of chronic copper toxicity is dependent on copper homeostasis and its tissue retention. Evidence from Wilson disease suggests that hepatic retention is indicative of potential future and possibly sudden onset of copper toxicity under conditions of continuous intake. Hence, emphasis was placed on copper retention as an early marker of potential adverse effects. The relationships between (a) chronic copper exposure and its retention in the body, particularly the liver, and (b) hepatic copper concentrations and evidence of toxicity were examined. The Scientific Committee (SC) concludes that no retention of copper is expected to occur with intake of 5 mg/day and established an Acceptable Daily Intake (ADI) of 0.07 mg/kg bw. A refined dietary exposure assessment was performed, assessing contribution from dietary and non-dietary sources. Background copper levels are a significant source of copper. The contribution of copper from its use as plant protection product (PPP), food and feed additives or fertilisers is negligible. The use of copper in fertilisers or PPPs contributes to copper accumulation in soil. Infant formula and follow-on formula are important contributors to dietary exposure of copper in infants and toddlers. Contribution from non-oral sources is negligible. Dietary exposure to total copper does not exceed the HBGV in adolescents, adults, elderly and the very elderly. Neither hepatic copper retention nor adverse effects are expected to occur from the estimated copper exposure in children due to higher nutrient requirements related to growth.

Cholinesterase Deficiency Syndrome-A Pitfall in the Use of Butyrylcholinesterase as a Biomarker for Wilson's Disease

A family is described as having two recessively inherited metabolic diseases and three differently affected children. During the explantation of a drain tube grommet under general anesthesia, a prolonged resuscitation and wake-up period occurred in the key case when he was 8 years old. This led to a family screening for butyrylcholinesterase deficiency, which was confirmed not only in the key case but also in his 5-year-old sister; it was not confirmed in his 10-year-old brother. However, the key case not only had reduced serum levels of BCHE, but also elevated liver enzyme levels, which are atypical for BCHE deficiency. After the exclusion of viral and autoimmune hepatitis, Wilson's disease (WD) was eventually diagnosed and also confirmed in his elder brother, but not in his sister. This family is presented to highlight an extremely rare WD-patient in whom a low serum level of BCHE did not occur because of WD but because of BCHE deficiency.

The Role of Zinc in the Treatment of Wilson’s Disease

Wilson’s disease (WD) is a hereditary disorder of copper metabolism, producing abnormally high levels of non-ceruloplasmin-bound copper, the determinant of the pathogenic process causing brain and hepatic damage and dysfunction. Although the disease is invariably fatal without medication, it is treatable and many of its adverse effects are reversible. Diagnosis is difficult due to the large range and severity of symptoms. A high index of suspicion is required as patients may have only a few of the many possible biomarkers. The genetic prevalence of ATP7B variants indicates higher rates in the population than are currently diagnosed. Treatments have evolved from chelators that reduce stored copper to zinc, which reduces the toxic levels of circulating non-ceruloplasmin-bound copper. Zinc induces intestinal metallothionein, which blocks copper absorption and increases excretion in the stools, resulting in an improvement in symptoms. Two meta-analyses and several large retrospective studies indicate that zinc is equally effective as chelators for the treatment of WD, with the advantages of a very low level of toxicity and only the minor side effect of gastric disturbance. Zinc is recommended as a first-line treatment for neurological presentations and is gaining acceptance for hepatic presentations. It is universally recommended for lifelong maintenance therapy and for presymptomatic WD.

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.

Biochemical diagnosis of Wilson's disease: an update

Wilson's disease (WD) is an inherited disorder of copper metabolism caused by mutations in the ATP7B gene. This condition is characterized by the accumulation of copper in the liver and other organs and tissues causing hepatic and neuropsychiatric manifestations. This paper reviews the diagnostic performance and limitations of the biochemical tests commonly used to detect this underdiagnosed disease. It also provides some recommendations and suggests a set of standardized laboratory comments. At present, a rapid, simple, reliable biochemical test that confirms diagnosis of WD is not available. However, diagnosis can be established based on serum ceruloplasmin and urinary copper excretion. Total serum copper should be employed with caution, since it has a low negative predictive value. The use of estimated non-ceruloplasmin-bound copper is not recommended. Nevertheless, measured relative exchangeable copper has very high sensitivity and specificity and emerges as a potential gold standard for the biochemical diagnosis of WD. The development of novel assays for WD detection makes this disorder a potential candidate to be included in newborn screening programs.

Clinical and genetic characterization of a large cohort of patients with Wilson’s disease in China

Background

Wilson’s disease (WD) is an autosomal recessive disorder of copper metabolism caused by ATP7B (encoding a copper-transporting P-type ATPase) variants that shows various characteristics according to race and geographical region. This study was aimed to provide a comprehensive analysis of ATP7B variants in China and to investigate a plausible role of common variants in WD manifestations.

Methods

A total of 1366 patients (1302 index patients and 64 siblings) clinically diagnosed with WD (Leipzig score ≥ 4) were recruited. They underwent ATP7B gene sequencing and information of age and symptoms at onset was collected. The genotype–phenotype correlation was assessed in the index patients who were examined with two pathogenic variants and onset with hepatic (n = 276) or neurologic (n = 665) symptoms.

Results

We identified 294 potentially pathogenic ATP7B variants (112 truncating, 174 missense, 8 in-frame) in the 1302 index patients, including 116 novel variants. The most frequent variant was c.2333G>T (R778L, allele frequency: 28.96%), followed by c.2975C>T (P992L, 13.82%), c.2621C>T (A874V, 5.99%), c.2755C>G (R919G, 2.46%), and c.3646G>A (V1216M, 1.92%). In 1167 patients, both pathogentic variants were identified, of which 532 different variant combinations were found. By binary logistic regression analysis, the factor associated with neurological presentation was high age-at-onset, but not sex, protein-truncating variant (PTV), or the common missense variants (R778L, P992L, and A874V). In the neurological group, low age-at-onset was a factor associated with dystonia, gait abnormality, and salivation; high age-at-onset was a factor associated with tremor; and the sex, low age-at-onset and A874V were independent factors associated with dysarthria. In addition, PTV, R778L, and P992L were predominant in early-onset patients, whereas A874V was predominant in late-onset patients, and patients with R778L/A874V genotype displayed a higher age-at-onset than patients with R778L/R778L or R778L/P992L genotype.

Conclusions

Our work expanded the ATP7B variant spectrum and highlighted the differences among patients with WD in age-at-onset and ATP7B variants, which may provide some valuable insights into the diagnosis, counseling, and treatment of patients with WD.

Wilson Disease Prevalence: Discrepancy Between Clinical Records, Registries and Mutation Carrier Frequency

OBJECTIVES

Diagnosis of Wilson disease (WD) is difficult and, as early detection may prevent all symptoms, it is essential to know the exact prevalence to evaluate the cost-efficacy of a screening program. As the number of WD patients was high in our population, we wished to estimate prevalence by determining the carrier frequency for clinically relevant ATP7B mutations.

METHODS

To estimate prevalence, screening for the most prevalent mutation was performed in 1661 individuals with ancestry in Gran Canaria, and the frequency of other mutations was estimated from patient records. Alternatively, ATP7B mutations were detected from exomes and genomes from 851 individuals with Canarian ancestry, 236 from Gran Canaria, and a public Spanish exome database.

RESULTS

Estimated carrier frequencies in Gran Canaria ranged from 1 in 20 to 28, depending on the method used, resulting in prevalences of 1 case per 1547 to 3140 inhabitants. Alternatively, the estimated affected frequencies were 1 in 5985 to 7980 and 1 in 6278 to 16,510 in the archipelago or mainland Spain respectively.

CONCLUSIONS

The number of carriers predicts much higher prevalences than reported, suggesting that WD is underdiagnosed; specific mutations may remain unnoticed due to low penetrance or no signs of disease at all; regional prevalence rather than national prevalence should be considered in cost-efficacy models to approach preventive screening in the asymptomatic population and genetic screening strategies will have to deal with the genetic heterogeneity of ATP7B in the general population and in patients.

Wilson's disease: update on pathogenesis, biomarkers and treatments

Wilson's disease is an autosomal-recessive disorder of copper metabolism caused by mutations in ATP7B and associated with neurological, psychiatric, ophthalmological and hepatic manifestations. Decoppering treatments are used to prevent disease progression and reduce symptoms, but neurological outcomes remain mixed. In this article, we review the current understanding of pathogenesis, biomarkers and treatments for Wilson's disease from the neurological perspective, with a focus on recent advances. The genetic and molecular mechanisms associated with ATP7B dysfunction have been well characterised, but despite extensive efforts to identify genotype-phenotype correlations, the reason why only some patients develop neurological or psychiatric features remains unclear. We discuss pathological processes through which copper accumulation leads to neurodegeneration, such as mitochondrial dysfunction, the role of brain iron metabolism and the broader concept of selective neuronal vulnerability in Wilson's disease. Delayed diagnoses continue to be a major problem for patients with neurological presentations. We highlight limitations in our current approach to making a diagnosis and novel diagnostic biomarkers, including the potential for newborn screening programmes. We describe recent progress in developing imaging and wet (fluid) biomarkers for neurological involvement, including findings from quantitative MRI and other neuroimaging studies, and the development of a semiquantitative scoring system for assessing radiological severity. Finally, we cover the use of established and novel chelating agents, paradoxical neurological worsening, and progress developing targeted molecular and gene therapy for Wilson's disease, before discussing future directions for translational research.

Movement Disorders and Liver Disease

The association of movement disorders with structural or functional hepatic disease occurs in three principal scenarios: (1) combined involvement of both organ systems from a single disease entity, (2) nervous system dysfunction resulting from exposure to toxic compounds in the setting of defective hepatic clearance, or (3) hepatic and/or neurological injury secondary to exposure to exogenous drugs or toxins. An important early step in the workup of any patient with combined movement disorders and liver disease is the exclusion of Wilson's disease. Diagnostic delay remains common for this treatable disorder, and this has major implications for patient outcomes. Thereafter, a structured approach integrating variables such as age of onset, tempo of progression, nature and severity of liver involvement, movement disorder phenomenology, exposure to drugs/toxins and laboratory/neuroimaging findings is key to ensuring timely diagnosis and disease‐specific therapy. Herein, we provide an overview of disorders which may manifest with a combination of movement disorders and liver disease, structured under the three headings as detailed above. In each section, the most common disorders are discussed, along with important clinical pearls, suggested diagnostic workup, differential diagnoses and where appropriate, treatment considerations.

Prevalence of Wilson disease based on genome databases in Japan

BACKGROUND

Wilson disease (WD) is an autosomal recessive disorder caused by mutations in the ATP7B gene. In 1984, Scheinberg and Sternlieb estimated the prevalence of WD to be 1:30 000. However, recent epidemiological studies have reported increasing prevalence rates in different populations. The carrier frequency of ATP7B variants and the prevalence of WD in the Japanese population have not been reported using multiple databases.

METHODS

Multiple public databases were used. First, we included mutations in the ATP7B gene that were registered in the Human Gene Mutation Database (HGMD) Professional, where 885 ATP7B variants were identified as pathogenic. Next, we investigated the allele frequencies of these 885 variants in Japanese individuals using the Human Genetic Variation Database (HGVD) and the Japanese Multi Omics Reference Panel (jMorp).

RESULTS

Of the 885 variants of ATP7B, 7 and 12 missense and nonsense variants, zero and three splicing variants, and zero and two small deletions were found in the HGVD and in jMorp, respectively. The total allele frequencies of the ATP7B mutations were 0.011 in the HGVD and 0.014 in the jMorp. According to these data, the carrier frequencies were 0.022 (2.2%) and 0.028 (2.8%), respectively, and patient frequencies were 0.000121 (1.21/10 000 individuals) and 0.000196 (1.96/10 000 individuals), respectively.

CONCLUSIONS

This is the first study to report the carrier frequency of ATP7B variants and the prevalence of WD in Japan using multiple databases. The calculated prevalence of WD was comparatively higher than that of previous reports, indicating previous underdiagnosis or the existence of less severe phenotypes.

Pathogenic gene variation spectrum and carrier screening for Wilson's disease in Qingdao area

Background

Despite the increasing number of reports on the analysis of ATP7B variants, reports on carrier screening for Wilson's disease (WD, OMIM:277900) are rare.

Methods

Peripheral blood samples were collected from 42 patients from Qingdao Women and Children's Hospital diagnosed with WD for direct sequencing of ATP7B gene. Twelve hotspot variants of ATP7B were selected for carrier screening in Qingdao area based on an analysis of information related to ATP7B variants and literature reports in China. We screened 5012 dried blood spots (DBSs) from asymptomatic newborns in Qingdao area to estimate carrier frequency. DNA was extracted from dried blood spots. Gene sequencing was performed using multiplex polymerase chain reaction (PCR) combined with second‐generation sequencing. The carrier frequency of each hotspot variant was calculated using the count data (expressed as number of carriers (%) obtained by direct counting.

Results

The carrier frequency of 12 hotspot variants was 1.46% (95% CI: 1.16–1.83%). The ATP7B variant with the highest carrier frequency was c.2333G>T, accounting for 54.79% of all variants screened, followed by c.2975C>T and c.2621C>T, accounting for 17.81% and 15.07% of all variants screened, respectively.

Conclusion

Carrier frequency of ATP7B gene pathogenic variants is high in the population in Qingdao area.

Estimating the clinical prevalence of Wilson's disease in the UK

Background & Aims

The clinical prevalence of Wilson’s disease (WD) in the UK remains unknown. The estimated genetic prevalence in the UK, 142/million, is higher than the clinical prevalence (15/million) reported in other European studies. The aim of this study was to estimate the clinical prevalence of WD utilising readily available laboratory and clinical data.

Method

Patients with WD who attended Nottingham University Hospital NHS Trust (NUH) between 2011 and 2018 were identified using multiple sources of case ascertainment: serum ceruloplasmin, 24-hour urinary copper, ‘Wilson’ in liver biopsy report, hospital prescription for penicillamine/trientine/zinc and admission coded with ICD-10 Code E83.0 (disorder of copper metabolism). Potential cases were identified using the Leipzig score, diagnosis was confirmed in hospital records and the point prevalence was calculated using the Office for National Statistics mid-2017 population estimates.

Results

A total of 1,794 patients were identified from ≥1 source; 19 patients had WD, of whom 11 were from within the study catchment area and alive at the time of point prevalence estimation. Twenty-nine patients had a Leipzig score ≥2 without a diagnosis of WD, but none had WD on screening (n = 16). The overall prevalence of WD was 15.5/million; males 16.9/million and females 14.1/million.

Conclusion

This is the first UK population-based study to assess the clinical prevalence of WD. The reported clinical prevalence is lower than the UK genetic prevalence, but comparable to the clinical prevalence reported in Europe. The case ascertainment approach used in this study may be cost-effective, and similar practises could be adopted nationally.

Lay summary

Our study estimates the clinical prevalence of Wilson’s disease, a rare genetic disorder of copper metabolism, in the UK. The estimated clinical prevalence is this study is markedly lower than the estimated UK genetic prevalence.

•

The clinical prevalence of Wilson’s disease in the UK is estimated to be 15.5/million (1/64,516).

•

The clinical prevalence is significantly lower than the previously reported genetic prevalence.

•

Routine clinical and laboratory data can be used to not only find existing cases, but also evaluate potential cases.

•

Case ascertainment is potentially a cost-effective approach for Wilson’s disease and other rare diseases.

Considerations for optimizing Wilson's disease patients' long-term follow-up

Wilson's disease is a sistemic genetic disease caused by the excessive accumulation of copper. The first and main involvement is in the liver, which can range from mild and transient elevation of transaminases to the onset of an overt cirrhosis or acute liver failure. It is known that up to 20-30% of these patients may evolve to liver cirrhosis during follow-up. In clinical practice, liver fibrosis is assessed mainly by using indirect and non-invasive tools (laboratory tests, liver elastography, ultrasound), similar to other prevalent chronic liver diseases. However, despite the fact that liver elastography is a valuable tool in general hepatology, the evidence of its usefulness and accuracy in Wilsońs disease is scarce. This review summarizes the available scientific data and their limitations in Wilson's disease.

Copper nutrition and biochemistry and human (patho)physiology

The essential trace mineral copper plays important roles in human physiology and pathophysiology. Disruption of copper homeostasis may underlie the development of ischemic heart disease, and connective tissue and neurodegenerative disorders. Copper also likely participates in the host response to bacterial infection and is further implicated more broadly in regulating immunity. Recent studies further associate copper with disruption of lipid homeostasis, as is frequently seen in, for example, non-alcoholic fatty liver disease (NAFLD). Moreover, continuing investigation of copper chaperones has revealed new roles for these intracellular copper-binding proteins. Despite these (and many other) significant advances, many questions related to copper biology remain unanswered. For example, what are the most sensitive and specific biomarkers of copper status, and which ones are useful in marginal (or "sub-clinical" copper deficiency)? Further research on this topic is required to inform future investigations of copper metabolism in humans (so the copper status of study participants can be fully appreciated). Also, are current recommendations for copper intake adequate? Recent studies suggest that overt copper deficiency is more common than once thought, and further, some have suggested that the copper RDAs for adults may be too low. Additional human balance and interventional studies are necessary and could provide the impetus for reconsidering the copper RDAs in the future. These and myriad other unresolved aspects of copper nutrition will undoubtedly be the focus of future investigation.

Wilson disease: revision of diagnostic criteria in a clinical series with great genetic homogeneity

BACKGROUND

Wilson disease is an autosomal recessive disorder of copper metabolism caused by mutations in the ATP7B gene. An early diagnosis is crucial to prevent evolution of the disease, as implantation of early therapeutic measures fully prevents its symptoms. As population genetics data predict a higher than initially expected prevalence, it was important to define the basic diagnostic tools to approach population screening.

METHODS

A highly genetically homogeneous cohort of 70 patients, belonging to 50 unrelated families, has been selected as a framework to analyze all their clinical, biochemical and genetic characteristics, to define the disease in our population, with an estimated prevalence of 1 in 12,369, and determine the most useful features that reach diagnostic value.

RESULTS

Serum ceruloplasmin below 11.5 mg/dL and cupremia below 60 μg/mL, were the best analytical predictors of the disease in asymptomatic individuals, while cupruria or hepatic copper determination were less powerful. Genetic analysis reached a conclusive diagnosis in all 65 patients available for complete testing. Of them, 48 were carriers of at least one p.Leu708Pro mutant allele, with 24 homozygotes. Nine patients carried a promoter deletion mutation, revealing that extended sequencing beyond the ATP7B gene-coding region is essential. All mutations caused hepatic damage since early ages, increasing its severity as diagnosis was delayed, and neurological symptoms appear.

CONCLUSION

Serum ceruloplasmin determination followed by genetic screening would reduce costs and favor the prioritization of non-invasive procedures to reach a definitive diagnosis, even for asymptomatic cases.

Wilson's Disease in Finland: A Nationwide Population-Based Study

BACKGROUND

Data on the epidemiology and prognosis of Wilson's disease are scarce, and no clinical data are available from Finland.

METHODS

All persons diagnosed and treated for Wilson's disease in Finnish hospitals in 1998 to 2017 were identified. Data were collected from national registries and patient charts.

RESULTS

The point prevalence was 0.45/100,000 (95% confidence interval, 0.29-0.67) on December 31, 2017, but no more than 0.35/100,000 (95% confidence interval, 0.21-0.55) among native Finns. Annual incidence was 0.016/100,000 (95% confidence interval, 0.0093-0.026). Median age at diagnosis was 15.8 years (interquartile range, 8.3-32.2; range, 3.8-48.1 years). Upon presentation, liver damage was observed in 58%, neurological signs and symptoms (most often tremor and dysarthria) in 40%, and 32% of patients were asymptomatic. Patients had poorer long-term survival (hazard ratio, 2.92 for death; P = 0.005) compared with matched controls.

CONCLUSIONS

Wilson's disease is very rare in Finland. Patients have an increased risk of death indicating an unmet treatment need. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.