Mutational analysis for Wilson's disease

Hepatitis B virus infection in patients with Wilson disease: A large retrospective study

BACKGROUND

Wilson disease (WD) is the most common genetic metabolic liver disease. Some studies have shown that comorbidities may have important effects on WD. Data on hepatitis B virus (HBV) infection in patients with WD are limited.

AIM

To investigate the prevalence and clinical impact of HBV infection in patients with WD.

METHODS

The clinical data of patients with WD were analyzed retrospectively, and the data of patients with concurrent WD and HBV infection were compared with those of patients with isolated WD.

RESULTS

Among a total of 915 WD patients recruited, the total prevalence of current and previous HBV infection was 2.1% [95% confidence interval (CI): 1.2%-3.0%] and 9.2% (95%CI: 7.3%-11.1%), respectively. The main finding of this study was the identification of 19 patients with concurrent WD and chronic hepatitis B (CHB) infection. The diagnosis of WD was missed in all but two patients with CHB infection. The mean delay in the diagnosis of WD in patients with concurrent WD and CHB infection was 32.5 mo, which was significantly longer than that in patients with isolated WD (10.5 mo). The rates of severe liver disease and mortality in patients with concurrent WD and CHB infection were significantly higher than those in patients with isolated WD (63.1% vs 19.3%, P = 0.000 and 36.8% vs 4.1%, P < 0.001, respectively). Binary logistic regression analysis revealed a significantly higher risk of severe liver disease at the diagnosis of WD in patients with current HBV infection [odds ratio (OR) = 7.748; 95%CI: 2.890-20.774; P = 0.000)] or previous HBV infection (OR = 5.525; 95%CI: 3.159-8.739; P = 0.000) than in patients with isolated WD.

CONCLUSION

The total prevalence of current HBV infection in patients with WD was 2.1%. The diagnosis of WD in CHB patients is usually missed. HBV infection is an independent risk factor for severe liver disease in WD patients. The diagnosis of WD should be ruled out in some patients with CHB infection.

Ending diagnostic odyssey using clinical whole-exome sequencing (CWES)

Objectives

Most rare diseases are genetic diseases. Due to the diversity of rare diseases and the high likelihood of patients with rare diseases to be undiagnosed or misdiagnosed, it is not unusual that these patients undergo a long diagnostic odyssey before they receive a definitive diagnosis. This situation presents a clear need to set up a dedicated clinical service to end the diagnostic odyssey of patients with rare diseases.

Methods

Therefore, in 2014, we started an Undiagnosed Diseases Program in Hong Kong with the aim of ending the diagnostic odyssey of patients and families with rare diseases by clinical whole-exome sequencing (CWES), who have not received a definitive diagnosis after extensive investigation.

Results

In this program, we have shown that genetic diseases diagnosed by CWES were different from that using traditional approaches indicating that CWES is an essential tool to diagnose rare diseases and ending diagnostic odysseys. In addition, we identified several novel genes responsible for monogenic diseases. These include the TOP2B gene for autism spectrum disorder, the DTYMK gene for severe cerebral atrophy, the KIF13A gene for a new mosaic ectodermal syndrome associated with hypomelanosis of Ito, and the CDC25B gene for a new syndrome of cardiomyopathy and endocrinopathy.

Conclusions

With the incorporation of CWES in an Undiagnosed Diseases Program, we have ended diagnostic odysseys of patients with rare diseases in Hong Kong in the past 7 years. In this program, we have shown that CWES is an essential tool to end diagnostic odysseys. With the declining cost of next-generation sequencers and reagents, CWES set-ups are now affordable for clinical laboratories. Indeed, owing to the increasing availability of CWES and treatment modalities for rare diseases, precedence can be given to both common and rare medical conditions.

Epidemiology and natural history of Wilson’s disease in the Chinese: A territory-based study in Hong Kong between 2000 and 2016

AIM

To investigate the epidemiology and natural history of Wilson’s disease in the Chinese.

METHODS

Data were retrieved via electronic search of hospital medical registry of the Hong Kong Hospital Authority, which covers all the public healthcare services. We identified cases of Wilson’s disease between 2000 and 2016 by the International Classification of Diseases (ICD)-9 code. We analyzed the incidence rate, prevalence and adverse outcomes of Wilson’s disease.

RESULTS

We identified 211 patients (male cases 104; female cases 107; median age 27.2 years, IQR: 17.1-38.6 years; duration of follow-up 8.0 years, IQR: 5.0-14.0 years). The average annual incidence rate was 1.44 per million person-years while the prevalence was 17.93 per million. Between 2000 and 2016, there was a decrease in the annual incidence rate from 1.65 to 1.23 per million person-years (P = 0.010), whereas there was an increase in the annual prevalence from 7.80 to 25.20 per million (P < 0.001). Among the 176 cases with hepatic involvement, 38 (21.6%) had cirrhosis, three (1.7%) developed hepatocellular carcinoma, 24 (13.6%) underwent liver transplantations, and 26 (14.8%) died. Seven patients had concomitant chronic viral hepatitis B or C. The 5-year and 10-years rates of overall survival were 92.6% and 89.5%, and for transplant-free survival rates 91.8% and 87.4%, respectively. Cirrhosis and possibly chronic viral hepatitis were associated with poorer overall survival.

CONCLUSION

There was a significant increase in the prevalence of Wilson’s disease in Hong Kong. The prognosis was favorable except for those with cirrhosis or concomitant viral hepatitis.

Inborn errors of metabolism and expanded newborn screening: review and update

Inborn errors of metabolism (IEM) are a phenotypically and genetically heterogeneous group of disorders caused by a defect in a metabolic pathway, leading to malfunctioning metabolism and/or the accumulation of toxic intermediate metabolites. To date, more than 1000 different IEM have been identified. While individually rare, the cumulative incidence has been shown to be upwards of 1 in 800. Clinical presentations are protean, complicating diagnostic pathways. IEM are present in all ethnic groups and across every age. Some IEM are amenable to treatment, with promising outcomes. However, high clinical suspicion alone is not sufficient to reduce morbidities and mortalities. In the last decade, due to the advent of tandem mass spectrometry, expanded newborn screening (NBS) has become a mandatory public health strategy in most developed and developing countries. The technology allows inexpensive simultaneous detection of more than 30 different metabolic disorders in one single blood spot specimen at a cost of about USD 10 per baby, with commendable analytical accuracy and precision. The sensitivity and specificity of this method can be up to 99% and 99.995%, respectively, for most amino acid disorders, organic acidemias, and fatty acid oxidation defects. Cost-effectiveness studies have confirmed that the savings achieved through the use of expanded NBS programs are significantly greater than the costs of implementation. The adverse effects of false positive results are negligible in view of the economic health benefits generated by expanded NBS and these could be minimized through increased education, better communication, and improved technologies. Local screening agencies should be given the autonomy to develop their screening programs in order to keep pace with international advancements. The development of biochemical genetics is closely linked with expanded NBS. With ongoing advancements in nanotechnology and molecular genomics, the field of biochemical genetics is still expanding rapidly. The potential of tandem mass spectrometry is extending to cover more disorders. Indeed, the use of genetic markers in T-cell receptor excision circles for severe combined immunodeficiency is one promising example. NBS represents the highest volume of genetic testing. It is more than a test and it warrants systematic healthcare service delivery across the pre-analytical, analytical, and post-analytical phases. There should be a comprehensive reporting system entailing genetic counselling as well as short-term and long-term follow-up. It is essential to integrate existing clinical IEM services with the expanded NBS program to enable close communication between the laboratory, clinicians, and allied health parties. In this review, we will discuss the history of IEM, its clinical presentations in children and adult patients, and its incidence among different ethnicities; the history and recent expansion of NBS, its cost-effectiveness, associated pros and cons, and the ethical issues that can arise; the analytical aspects of tandem mass spectrometry and post-analytical perspectives regarding result interpretation.

Pathogenesis and management of Wilson disease

Hepatolenticular degeneration, commonly known as Wilson disease, is an autosomal recessive inherited disease of abnormal copper metabolism, characterized by the accumulation of copper in the body due to decreased biliary excretion of copper from hepatocytes. Wilson disease protein, ATP7B, functions in copper excretion into bile and in copper secretion to the bloodstream coupled with ceruloplasmin synthesis. Various kinds of mutations of ATP7B cause Wilson disease. Wilson disease is a rare genetic disease that can be treated pharmacologically. Recognition and prompt diagnosis are very important, because Wilson disease is fatal if left untreated. In this review, I summarize the pathogenesis and management of Wilson disease.

A genetic study of Wilson's disease in the United Kingdom

Previous studies have failed to identify mutations in the Wilson's disease gene ATP7B in a significant number of clinically diagnosed cases. This has led to concerns about genetic heterogeneity for this condition but also suggested the presence of unusual mutational mechanisms. We now present our findings in 181 patients from the United Kingdom with clinically and biochemically confirmed Wilson's disease. A total of 116 different ATP7B mutations were detected, 32 of which are novel. The overall mutation detection frequency was 98%. The likelihood of mutations in genes other than ATP7B causing a Wilson's disease phenotype is therefore very low. We report the first cases with Wilson's disease due to segmental uniparental isodisomy as well as three patients with three ATP7B mutations and three families with Wilson's disease in two consecutive generations. We determined the genetic prevalence of Wilson's disease in the United Kingdom by sequencing the entire coding region and adjacent splice sites of ATP7B in 1000 control subjects. The frequency of all single nucleotide variants with in silico evidence of pathogenicity (Class 1 variant) was 0.056 or 0.040 if only those single nucleotide variants that had previously been reported as mutations in patients with Wilson's disease were included in the analysis (Class 2 variant). The frequency of heterozygote, putative or definite disease-associated ATP7B mutations was therefore considerably higher than the previously reported occurrence of 1:90 (or 0.011) for heterozygote ATP7B mutation carriers in the general population (P < 2.2 × 10(-16) for Class 1 variants or P < 5 × 10(-11) for Class 2 variants only). Subsequent exclusion of four Class 2 variants without additional in silico evidence of pathogenicity led to a further reduction of the mutation frequency to 0.024. Using this most conservative approach, the calculated frequency of individuals predicted to carry two mutant pathogenic ATP7B alleles is 1:7026 and thus still considerably higher than the typically reported prevalence of Wilson's disease of 1:30 000 (P = 0.00093). Our study provides strong evidence for monogenic inheritance of Wilson's disease. It also has major implications for ATP7B analysis in clinical practice, namely the need to consider unusual genetic mechanisms such as uniparental disomy or the possible presence of three ATP7B mutations. The marked discrepancy between the genetic prevalence and the number of clinically diagnosed cases of Wilson's disease may be due to both reduced penetrance of ATP7B mutations and failure to diagnose patients with this eminently treatable disorder.

Wilson disease in 71 patients followed for over two decades in a tertiary center in Saudi Arabia: a retrospective review

BACKGROUND AND OBJECTIVES

Wilson disease (WD) is a rare autosomal recessive disease. Our objective was to describe the diverse patterns, therapies, and outcomes of this disease.

DESIGN AND SETTING

A retrospective study over two decades on WD patients in a tertiary care center in Saudi Arabia.

PATIENTS AND METHODS

Clinical and laboratory findings of 71 patients with WD were retrieved from their charts, referral notes and our hospital electronic records and were analyzed.

RESULTS

The mean age and standard deviation was 16.8 (10.7) years and 56.5% were males. The main manifestations of WD were hepatic, neurological, and mixed in 39 (54.9%), 12 (16.9%), and 20 (28.2%) patients, respectively, and 11 (15.5%) were asymptomatic cases detected by family screening. A family history of WD was positive in 41 (57.7%) patients, and consanguinity of parents was found in 26 (36.6%) patients. The mean (SD) follow-up period was 92.2 (72.9) (range, 1-320) months. Ten (14.1%) patients died during follow up, while 45 (63.4%) and 16 (22.5%) were still on or lost from follow-up, respectively. The mean (SD) age at the end of follow-up was 25.3 (12) (range, 4-62) years. Hepatoma was discovered in 5 (7.0%) patients. Penicillamine therapy was used by 58 (81.7%) patients, while zinc and trientine were given to 32 (45.1%) and 11 (15.5%) patients, respectively. Sixteen (22.5%) patients underwent liver transplantation and one died (1.4%) on the waiting list. The liver condition remained stable or improved in 35 (49.3%), and the neurological status showed improvement in 11 (34.4%) of the 32 patients who had neurological involvement.

CONCLUSIONS

This is the biggest cohort to be reported from the Middle East. WD presentation and outcome of WD are very diverse, and its diagnosis still depends on clinical, laboratory, and radiological evidence of abnormal copper metabolism. WD should be considered in patients of any age with obscure hepatic and/or neurological abnormalities.

Clinical and molecular characterization of Wilson's disease in China: identification of 14 novel mutations

BACKGROUND

Wilson's disease (WND) is a rare autosomal recessive disorder. Here we have evaluated 62 WND cases (58 probands) from the Chinese Han population to expand our knowledge of ATP7B mutations and to more completely characterize WND in China.

METHODS

the coding and promoter regions of the ATP7B gene were analyzed by direct sequencing in 62 Chinese patients (58 probands) with WND (male, n = 37; female, n = 25; age range, 2 ~ 61 years old).

RESULTS

neurologic manifestations were associated with older age at diagnosis (p < 0.0001) and longer diagnostic delay (p < 0.0001). Age at diagnosis was also correlated with urinary copper concentration (r = 0.58, p < 0.001). Forty different mutations, including 14 novel mutations, were identified in these patients. Common mutations included p.Arg778Leu (31.9%) and p.Pro992Leu (11.2%). Homozygous p.Arg778Leu and nonsense mutation/frameshift mutations were more often associated with primary hepatic manifestations (p = 0.0286 and p = 0.0383, respectively) and higher alanine transaminase levels at diagnosis (p = 0.0361 and p = 0.0047, respectively). Nonsense mutation/frameshift mutations were also associated with lower serum ceruloplasmin (p = 0.0065).

CONCLUSIONS

we identified 14 novel mutations and found that the spectrum of mutations of ATP7B in China is quite distinct from that of Western countries. The mutation type plays a role in predicting clinical manifestations. Genetic testing is a valuable tool to detect WND in young children, especially in patients younger than 8 years old. Four exons (8, 12, 13, and 16) and two mutations (p.Arg778Leu, p.Pro992Leu) should be considered high priority for cost-effective testing in China.