What makes a condition rare?
There are different definitions of rare disease. Some experts think a disease is rare if it affects only a certain number of people out of every thousand, while others may consider a condition rare because it’s caused by a specific gene, for example.
It can also depend on where you live in the world, your ethnicity or your age – a disease might be rare in one area or group of people, but more common in others.
In general, though, a condition is usually considered rare if it affects fewer than 1 in 2000 people in the general population.
Some diseases are so unusual they may affect far fewer people than this, though.
There are a lot of rare diseases – over 6000 are known at the moment, and more are being defined all the time. So this means that around 3.5 million people in the UK – 1 in 17 – will be affected by a rare disease at some point in their lives. Many rare conditions are genetic, and often they’re long-term (chronic) conditions.
How many people have a rare kidney condition?
Around 70 in 100,000 people have a rare kidney condition.
Of kidney patients, more than 10% of adults and nearly all children with end-stage kidney disease have a rare kidney disease, and at least 3 in 5 children and 1 in 9 adults having renal replacement therapy have end-stage kidney disease due to rare disease.
Rare kidney conditions: getting a diagnosis
On average, it takes four years for a rare disease to be diagnosed. But for some people, it could take much longer.
On the other hand, certain conditions, such as autosomal recessive polycystic kidney disease (ARPKD), may present in childhood, or even in the womb, when scans show a baby isn’t developing normally.
Conditions that present early are often very serious. If a doctor spots a pattern of symptoms that might suggest a genetic condition, a disease may be diagnosed through genetic testing, which is improving all the time.
Sometimes, it may be the standard tests for kidney conditions that pick up the first signs of a problem.
How are rare kidney conditions treated?
With common conditions, doctors have a good idea of the course of the disease and how to manage it, but with a rare disease, they may not see enough people to know how it’s likely to develop. So it may be a question of treating the symptoms, even if doctors don’t know exactly what’s happening in your body to cause them. Sometimes, this may mean that treatment and management are the same as for more common kidney conditions.
If you’re not diagnosed until you have symptoms, you may need to start dialysis straight away and go onto the transplant waiting list. Transplant may be a cure, depending on the condition you have, but sometimes the underlying condition will eventually damage a new kidney.
Some rare kidney conditions can be managed, at least partly, through having a healthy lifestyle, blood pressure medication and regular monitoring.
Dietary changes are needed with some conditions, such as Bartter syndrome, which cause the body to lose salt, so you need a high-salt diet, under the guidance of a specialist dietitian.
How are rare kidney conditions researched?
Research doesn’t tend to happen in a smooth line. Progress may be slow for a long time, as so few people are affected by some of these conditions, meaning there’s little expertise available. But sometimes, scientists may suddenly discover something that can very quickly change the way a condition is treated.
It can take years for new medications to be approved but researchers may investigate whether drugs already licensed to treat something else can help with rare kidney diseases. For example, blood pressure medications may be tried for kidney disease. And there’s lots of research into infusions of a drug called eculuzimab, usually prescribed for autoimmune conditions, as a treatment for atypical haemolytic uraemic syndrome (aHUS).
What’s RaDaR and what are the benefits of joining?
The National Registry of Rare Kidney Diseases – or RaDaR – is an initiative run by the UK Kidney Association.
RaDaR aims to pull together patients’ medical information, including blood and urine results, kidney function and medications, in order to build up knowledge. By joining, you contribute to that bank of knowledge – and you can be contacted about research studies, which may involve trying new drugs. You’ll also get invited to patient information events. So joining could help others with your condition, and you, or your child. Talk to your doctor if you’re interested.