John Terry, Cystinosis Foundation UK
The Fourth International Cystinosis Conference was held in Noordwijkerhout in the Netherlands on the weekend 30 June to 2 July. I went with Jonathan and his mother, June, and attended the medical/scientific sessions. For some of these there were parallel sessions on family issues but I cannot report on those.
The Conference was attended by 200 delegates (doctors, researchers and families) from 4 continents. These meetings, which occur every other year, are a great experience and I do recommend that everyone tries to attend at least one. So much happens away from the formal meetings: friendships are formed and informal consultations with the most experienced Cystinosis doctors in the world are possible and do occur.
But, what of the technical meetings? The main message from this conference is KEEP TAKING YOUR CYSTAGON! Various studies were reported and these indicated that the dosage level is critical but that the correct dosage is no good without 100% compliance. Particularly with adolescents, compliance is a major issue and some believe that it is the reason why, even for patients who have had the drug since infancy, transplantation is needed in late teens or early twenties.
The reasons why adolescents in particular do not always take their doses are obvious: the taste and, particularly, the odour of the cysteamine with its social implications. Work was reported from the USA by R Dohil, University of San Diego, on an investigation of an enteric coating of the cysteamine active to prevent it dissolving in the stomach but designed to release in the smallintestine. As presented the results showed the release of the cysteamine into the blood was delayed but the levels were unchanged. (There was also mention of activity in Germany where a local pharmacist had added a coating to the Cystagon capsules to try to achieve the same thing with bad results: the capsules passed through without releasing at all. Uncontrolled experiments like that are most dangerous). In the UK two groups are working on ‘prodrug’ approaches to the problem. The Cystinosis Foundation UK is supporting work led by Roz Anderson at Sunderland University which is making great progress. Their approach is to attach other chemical groups to the cysteamine molecule to create tasteless, odourless soluble compounds which will be transported by the blood stream to the cells where they will be broken down by enzymes on the cell walls to release the cysteamine where it is needed. In Aberdeen, work by Don Cairns takes a different approach. They are making insoluble compounds of cysteamine so that they will not dissolve in the saliva or break down in the gastro-intestinal tract but are intended to deliver the cysteamine in the intracellular fluid. If successful, either prodrug approach could lead to a greatly reduced dosage level because the active cysteamine will not be lost through excretion.
Dosage level has become an issue because of some recent events. Four patients developed strange ‘bruising’ on their elbows. These were red, raised lumps and the mechanism of their formation is still unclear. Unfortunately, one child had similar formations in his brain which led to his death. It has recently been revealed that there have been two cases before so there are a total of six. Although particularly high dose levels of Cystagon were present in some cases, it is not clear that this is true in all. William van’t Hoff, president of the Cystinosis Foundation UK, reported that the specialists have agreed that there should be a change from a dose based on weight to one based on area, found from a chart of height versus weight. I understood that there is no suggestion that long term patients should reduce their dose, but the important thing is that everyone should be aware of the issue and at any sign of bruising, unusual bone pain or weakness reduce the Cystagon intake and consult your doctor.
What of gene therapy? The message here is that if it does come, it is a long way off. Papers were presented that demonstrated that all cystinotics do not have the same gene defect. The one common in Northern Europe is not present at all in patients in Turkey, for example, although the defects are on the same chromosome.
In France, two groups have been studying cystinotic mice. They exhibit some of the same symptoms as human patients but do not suffer kidney failure, so it is unclear how much value these studies are going to give. One of their characteristics is inferior ‘working memory’. Studies by Doris Trauner in the USA have found that children with Cystinosis can have difficulties with visual memory, visual-motor skills and visual attention. Their intelligence levels are normal, however. Using MRI scans the problems have been associated with differences from normal children in the brain structure.
Studies of renal bone disease, reported by Craig Langman of North Western University in the USA, have led to the issue of new recommendations for the treatment of children with kidney failure.
This has been a review of the papers that I found particularly interesting. Others described most elegantly why in kidney failure children exhibit the symptoms they do, why muscle wastage in older cystinotics is a problem leading, in particular, to swallowing difficulties. For this, once again, long term treatment with Cystagon will help.
I have not mentioned eye problems, but the message there is that cysteamine eye drops are effective if used as directed.
The breadth of work going on to study different aspects of Cystinosis is very encouraging. In his closing address, William van’t Hoff stated that 1,220 papers had been published on aspects of Cystinosis in the last 18 years. That indicates a lot of activity for such a rare condition. He also mentioned that there was a high level of collaboration between doctors working on Cystinosis and much better than many other diseases. Finally, I say again, KEEP TAKING YOUR CYSTAGON.
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