Category: GENERAL

In all fairness, neurologists only very rarely come across patients with Wilson’s disease. This disorder of excessive copper deposition in tissues is however not vanishingly rare. And because it is one of the few curable neurological disorders, it is drummed into the brain of every neurologist to consider Wilson’s disease in any person, at any age, with any movement disorder. Dystonia is probably the most characteristic movement disorder in Wilson’s disease, and one of its classical signs is rhisus sardonicus, a fixed vacuous smile (which, by the way, may also be seen in tetanus). Other movement disorders of Wilson’s disease include parkinsonism, wing-beating tremor, ataxia, myoclonus, chorea, athetosis, stereotypies, tics, and restless legs syndrome. It is therefore not surprising that the disorder is named after one of neurology’s greats, Samuel Alexander Kinnier Wilson.

The other name for Wilson’s disease is hepatolenticular degeneration. ‘Lenticular’ in this context refers to the favoured brain targets of Wilson’s disease, the lentiform nuclei. These are the putamen and globus pallidus, which, along with the caudate nucleus, make up the basal ganglia. The basal ganglia are very important in the coordination of movement, and are also dysfunctional in disorders such as Huntington’s disease and Parkinson’s disease.

Wilson’s disease is however more than a brain disorder because it is, quintessentially, multi-systemic. The monicker hepatolenticular, for example, hints at the prominent and varied involvement of the liver in Wilson’s disease. Liver dysfunction here ranges from mild elevation of liver enzymes, to frank hepatic failure requiring liver transplantation. The eye is another important organ targeted by Wilson’s disease, and the neurologist is ever searching for the tell-tale but elusive Kayser-Fleischer ring. This is a brownish tinge seen around the iris caused by copper deposition, and named after the German ophthalmologists Bernhard Kayser and Bruno Fleischer. Another distinctive eye sign in Wilson’s disease is the sunflower cataract. The long reach of Wilson’s disease however extends to almost every organ system.

Wilson’s disease is all about the ‘C’ words. The first ‘C’, Copper, is of course the essential element recognised as Cu, with atomic number 29, and snugly occupying group 4 in the periodic table. An autosomal recessive genetic mutation in ATP7B, the copper transporter gene, means some people are unable to move copper around the body. It therefore accumulates, and is eventually deposited, in almost every organ. Oh, and it also overflows in high amounts in urine.

The other ‘C’ word is Ceruloplasmin, the blood protein that binds up the dangerous free-floating copper in the blood. The blood level of ceruloplasmin is low in Wilson’s disease because it is overwhelmed by the massive amounts of copper. The classical laboratory features of Wilson’s disease are therefore raised blood copper, low blood ceruloplasmin, and elevated 24 hour urinary copper excretion. The diagnosis of Wilson’s disease may also involve a liver biopsy to confirm copper accumulation, but this is rarely required. Long-term treatment depends on one of several therapeutic options for chelating or binding copper. Surveillance requires a tight monitoring regime to monitor the metabolic profile of the disease, and the complications its treatment.

Is it however not all and dusted for Wilson’s disease. Not at all. There are advances being made to simplify the diagnosis and monitoring of this devastating disease, and below are 5 exciting developments in the management of Wilson’s disease.

Exchangeable copper

I learnt of this from a paper published in the European Journal of Neurology titled Exchangeable copper: a reflection of the neurological severity in Wilson’s disease. The authors, Aurelia Poujois and colleagues, investigated this new technique of measuring exchangeable copper (CuEXC) as an aid to the diagnosis of Wilson’s disease, and as an indicator of the severity of extra-hepatic damage. They studied 48 newly diagnosed subjects and found that CuEXC is a reliable test for making the diagnosis, and a cut-off value of >2.08 μmol/l is a marker of severe organ damage. Other papers have confirmed the value of exchangeable copper, even if they call it relative exchangeable copper.

X-ray fluorescence

Slávka Kaščáková and colleagues, in their paper published in the journal Pathology, touted X-ray fluorescence as a rapid way to quantify copper in tissues, thereby facilitating the diagnosis of Wilson’s disease. The rather technical paper, titled Rapid and reliable diagnosis of Wilson disease using X-ray fluorescence, describes the technique as ‘high‐resolution mapping of tissue sections’ which enables the measurement of ‘the intensity and the distribution of copper, iron and zinc while preserving the morphology’. This technique can, we have to accept, reliably distinguish Wilson’s disease from other diseases such as haemochromatosis and alcoholic cirrhosis. Not a bad deal, but the squeamish neurologist must realise it requires a liver biopsy!

Quantitative transcranial ultrasound

The typical method of ‘seeing’ the brain abnormalities of Wilson’s disease is by magnetic resonance imaging (MRI). Ultrasound is however much cheaper and easier, and would be a preferable option if it can be shown to be sensitive and specific. And this is what Gotthard Tribl and colleagues demonstrated in their paper published in the Journal of Neurological Sciences titled Quantitative transcranial sonography in Wilson’s disease and healthy controls: cut-off values and functional correlates. They reported that in Wilson’s disease, the lenticular nuclei (we are familiar with this now) and substantia nigra (literally a black substance in the midbrain) are hyperechogenic compared to normal control subjects. They also came up with reliable cut-off for normality. To make things better, the thalami and midbrain are also hyperechogenic. And to add the cherry on top, the third ventricle is enlarged. More than expected from a rather simple technology.

Optical coherence tomography (OCT)

Hardly a day goes by that one doesn’t read a report on the applicability of optical coherence tomography (OCT) in one neurological disorder or the other. And Wilson’s disease is clearly not going to be the exception. OCT simply assesses the thickness or density of the retinal nerve fiber layer (RNFL), and this is reduced in many neurodegenerative diseases. In their paper titled Optical coherence tomography as a marker of neurodegeneration in patients with Wilson’s disease, Ewa Langwińska-Wośko and colleagues studied 58 subjects with Wilson’s disease. They reported that OCT can reliably measure the severity of Wilson’s disease, and it may reliably monitor disease progression. Another simple and non-invasive tool with big potential. 

Bis-choline tetrathiomolybdate

The treatment of Wilson’s disease centres on chelation or binding of copper. And the three major players here are  Penicillamine, Trientine, and Zinc, each with its own unique advantages and serious complications. They are however all rather cumbersome and inconvenient to administer and monitor. Into this unsatisfactory situation enters a study which promises to ease the burden for neurologist and patient. The trial is titled Bis-choline tetrathiomolybdate in patients with Wilson’s disease: an open-label, multicentre, phase 2 study, and it is published in the journal Lancet Gastroenterology and Hepatology. The authors, Karl Heinz Weiss and colleagues, investigated bis-choline tetrathiomolybdate (nicknamed WTX101), which they described as ‘an oral first-in-class copper-protein-binding molecule’. It binds up copper that is either stuck in the liver or swimming freely in blood. 70% of the 28 subjects they treated met the criteria for treatment success, and they were not unduly bothered by any nasty side effects. To add to this favourable profile, WTX101 has the convenience of a once daily dosing regime.

 

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It is reassuring that so much as happening at the cutting edge of Wilson’s disease, and neurologists can’t wait to see when these will form part of their armamentarium.