Association of Variants in the CP, ATOX1 and COMMD1 Genes with Wilson Disease Symptoms in Latvia

An Effort to Identify Genetic Determinants in Siblings With Wilson Disease Manifesting Striking Clinical Heterogeneity: An Exome Profiling Study of Two Indian Families

BACKGROUND

Wilson disease (WD) is a rare autosomal recessive disorder of copper metabolism caused due to mutations in the copper transporter ATP7B. There is often a striking variability of clinical manifestations among patients with ATP7B mutations, including in siblings. This phenomenon may be caused by individual differences in copper accumulation in hepatocytes and intolerance to copper toxicity as governed by genetic variations in copper metabolism genes acting as modifier loci to the disease.

OBJECTIVE

To elucidate the genetic basis of striking clinical heterogeneity among two siblings of two families with WD.

METHODS

The disease diagnosis and subsequent clinical examinations were performed by expert clinicians. The younger siblings in both families presented with early neurological manifestations at a younger age than their older siblings. Interestingly, only the younger siblings were reported to have had hepatic manifestations. Exome sequencing of all the four individuals was performed to understand their heterogeneous phenotypic outcomes.

RESULTS

Genetic screening revealed no difference in the ATP7B variant spectrum between the siblings of each family. However, the siblings of both the families were found to harbor mutually exclusive pathogenic variants in suspected modifier genes implicated in copper metabolism and/or other neurological and hepatic disorders having overlapping symptoms with WD, viz., CFTR, PPARG, ABCB11, ATP7A, CYP2D6, mTOR, TOR1A, and CP, which can potentially explain their differential clinical phenotypes.

CONCLUSION

Clinical heterogeneity between siblings with WD with the same ATP7B mutation profile may be attributed to the presence of different pathogenic variants in potential modifier genes.

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.

Biochemical testing for the diagnosis of Wilson's disease: A systematic review

Background

Wilson's disease (WD) is a rare inherited disorder that leads to copper accumulation in the liver, brain, and other organs. WD is prevalent worldwide, with an occurrence of 1 per 30,000 live births. Currently, there is no gold standard diagnostic test for WD. The objective of this systematic review is to determine the diagnostic accuracy for WD of three biochemical tests, namely hepatic copper, 24‐hour urinary copper, and ceruloplasmin using the Leipzig criteria.

Methods

Adhering to PRISMA guidelines, databases including PubMed/MEDLINE, CINAHL Plus, Web of Science, and Cochrane were searched. Studies that comprised of confirmed or suspected WD along with normal populations were included with adult and pediatric group. The sensitivity, specificity, negative predictive value and positive predictive value were computed using RevMan 5.4.

Results

Nine studies were included. The best practice evidence for 24‐hour urinary copper test ranged from a cutoff value of 0.64–1.6 μmol/24 h (N = 268; sensitivity = 75.6%, specificity = 98.3%). Hepatic copper test was optimally cutoff based on the ROC curve analysis at 1.2 μmol/g yielding a power of 96.4% sensitivity and 95.4% specificity (N = 1,150); however, the tried and tested 4 μmol/g cutoff, with 99.4% sensitivity and 96.1% specificity, is more widely accepted. The ceruloplasmin test cutoff value was found to be ranging from 0.14 to 0.2 g/L (N = 4,281; sensitivity = 77.1%–99%, specificity = 55.9%–82.8%).

Conclusion

This paper provides a large‐scale analysis of current evidence pertaining to the biochemical diagnosis of WD employing the Leipzig criteria. The laboratory values are typically based on specific subgroups based on age, ethnicity, and clinical subgroups. The findings of this systematic review must be used with caution, given the over‐ or under‐estimation of the index tests.