Neurological Wilson's disease lethal for the son, asymptomatic in the father

Wilson's Disease: Facing the Challenge of Diagnosing a Rare Disease

Wilson disease (WD) is a rare disorder caused by mutations in ATP7B, which leads to the defective biliary excretion of copper. The subsequent gradual accumulation of copper in different organs produces an extremely variable clinical picture, which comprises hepatic, neurological psychiatric, ophthalmological, and other disturbances. WD has a specific treatment, so that early diagnosis is crucial to avoid disease progression and its devastating consequences. The clinical diagnosis is based on the Leipzig score, which considers clinical, histological, biochemical, and genetic data. However, even patients with an initial WD diagnosis based on a high Leipzig score may harbor other conditions that mimic the WD's phenotype (Wilson-like). Many patients are diagnosed using current available methods, but others remain in an uncertain area because of bordering ceruloplasmin levels, inconclusive genetic findings and unclear phenotypes. Currently, the available biomarkers for WD are ceruloplasmin and copper in the liver or in 24 h urine, but they are not solid enough. Therefore, the characterization of biomarkers that allow us to anticipate the evolution of the disease and the monitoring of new drugs is essential to improve its diagnosis and prognosis.

Are the new genetic tools for diagnosis of Wilson disease helpful in clinical practice?

The diagnosis of Wilson disease is not always easy. For many patients, a combination of tests reflecting disturbed copper metabolism may be needed. Testing for ATP7B variants has become part of the routine diagnostic approach. The methods of genetic testing include analysis of the 21 coding exons and intronic flanking sequences, in which exons with recurrent variants would be prioritised depending on the mutation frequency in the local population. If sequencing the entire ATP7B gene cannot identify 2 variants and the suspicion for Wilson disease is high, after reviewing the clinical data, WES (whole-exome sequencing) or WGS (whole-genome sequencing) could be applied. A workflow based on the type and number of ATP7B variants responsible for Wilson disease is proposed. Genetic testing is indicated for confirmation of diagnosis, family screening, and screening of newborns and infants and in unclear cases suspected of suffering from Wilson disease. However, genetic testing is not a routine screening test for Wilson disease. If no additional variants can be identified, it can be assumed that other hereditary disorders may mimic Wilson disease (congenital disorders of glycosylation, MEDNIK syndrome, idiopathic or primary copper toxicoses).

Challenges in the diagnosis of Wilson disease

The understanding and management of Wilson disease (WD) have dramatically improved since the first description of the disease by K. Wilson more than a century ago. However, the persistent long delay between the first symptoms and diagnosis emphasizes challenges in diagnosing earlier this copper overload disorder. As a treatable disease, WD should be detected early in the course of the disease by any health professionals at any care level, but the rare prevalence of the disease explains the lack of awareness of referring physicians. The most important challenge is to train physicians to recognize atypical or rare symptoms of WD that will lead to discuss the diagnosis more systematically. Atypia can come from the age of onset, the liver [non-alcoholic steatohepatitis (NASH) presentation], the central or peripheral nervous system (neuropathy, epilepsy, sleep disorders…) or may be due to lesions of other organs (renal manifestations, osteo-articular disorders or endocrine disturbances). Isolated biological anomalies, rare radiological findings or inadequate interpretation of copper test may also lead to misdiagnosis. The second challenge is to confirm the diagnosis faster and more effectively so as not to delay the initiation of treatment, and expand family screening as the genetic prevalence is higher than previously expected. Generalization of the exchangeable copper assay and the next generation sequencing (NGS) are two promising ways to overcome this ultimate challenge. By drawing attention to the earliest and rare symptoms and to new biomarkers and diagnostic tools, we hope that this article will increase diagnostic awareness and reduce delays so that patients can start their treatment earlier in the course of the illness and thus have a better disease prognosis.

Wilson's disease: A 2017 update

Wilson's disease (WD) is characterised by a deleterious accumulation of copper in the liver and brain. It is one of those rare genetic disorders that benefits from effective and lifelong treatments that have dramatically transformed the prognosis of the disease. In Europe, its clinical prevalence is estimated at between 1.2 and 2/100,000 but the genetic prevalence is higher, at around 1/7000. Incomplete penetrance of the gene or the presence of modifier genes may account for the difference between the calculated genetic prevalence and the number of patients diagnosed with WD. The clinical spectrum of WD is broader as expected with mild clinical presentations and late onset of the disease after the age of 40 in 6% of patients. WD is usually suspected when ceruloplasmin and serum copper levels are low and 24h urinary copper excretion is elevated. Recently, a major diagnostic advance was achieved with implementation of the direct assay of "free copper", or exchangeable copper (CuEXC). The relative exchangeable copper (REC) that corresponds to the ratio between CuEXC and total serum copper enables a diagnosis of WD with high sensitivity and specificity when REC>18.5%. Moreover, CuEXC values at diagnosis are a marker of extrahepatic involvement and its severity. A value of >2.08μmol/L is suggestive of corneal and brain involvement (Se=86%, Sp=94%), and the disease will be more clinically and radiologically severe as values rise. The use of FibroScan^® is becoming more widespread to assess liver stiffness measurements in WD patients. 6.6kPa is considered to be a threshold value between mild and moderate fibrosis, whereas a value higher than 8.4 is indicative of severe fibrosis. More studies are now necessary to confirm the usefulness of Fibroscan^® in managing chronic therapy for WD patients. Treatment of this disease is based on an initial active and prolonged chelating phase (with D-Penicillamine or Trientine) followed by maintenance with Trientine or zinc salt. The two major problems that may be encountered are neurological worsening during the initial phase and non-compliance with treatment during maintenance therapy. Liver transplantation is the recommended therapeutic option in WD with acute liver failure or end-stage liver cirrhosis; its indication should be considered when neurological status deteriorates rapidly despite effective chelation. Regular clinical, biological and liver ultrasound follow-up is essential to evaluate efficacy, tolerance and treatment compliance, but also to detect the onset of hepatocellular carcinoma on a cirrhotic liver. There are hopes in the near future with the introduction of a new chelator and inhibitor of copper absorption, tetrathiomolybdate (TTM) and the development of gene therapy.

Relative exchangeable copper: a promising tool for family screening in Wilson disease

BACKGROUND

Family screening is a main step for the diagnosis in Wilson disease. This study was undertaken to evaluate the value of relative exchangeable copper for family screening.

METHODS

Data from family screening were collected from the French National Center of Reference for Wilson disease. Subjects who were first- or second-degree relatives of the index case underwent clinical examination and biological parameters.

RESULTS

Of 127 subjects examined, copper abnormalities or low ceruloplasminemia were detected in 21 subjects, corresponding to 5 patients with Wilson disease, 14 heterozygous ATP7B carriers and 2 subjects with no ATP7B mutations. Relative exchangeable copper determination significantly discriminates heterozygous ATP7B carriers and subjects with no ATP7B mutations from WD patients with a cutoff of 15%.

CONCLUSIONS

Exchangeable copper appears to be a promising tool for family screening in Wilson disease.