Not the one and only in 2020


Article No. 309

10 January 2020

At the end of next month it will be Rare Disease Day 2020.
”So what!?”
“So what?” Whilst I can understand your reaction , as awareness days as well as weeks or months are commonplace these days and are somewhat old fashioned it is still of importance to the estimated 270 million to  380 million people around the world affected by the 6000 to 8000 rare diseases.
 A difference of over 100 million people!? Clearly you don’t how many people have a rare disease and you don’t how many rare diseases there are too, is that right? But you do know what a rare disease is though, don’t you”
Good question because actually there is  no consensus of when a disease becomes rare.
“No consensus?”
Yes there are several definitions based on numbers of people affected. In USA a disease is considered rare if there are less than 200,000 of the population affected by it ( around 1 in 1500 people). In Japan a disease is rare if  fewer than 50,000 people are affected ( about 1  in 2500 people). For  Europe the figure is 5 in 10,000  (1 in 2000), but Europe excludes any rare disease which is not life threatening , nor chronically debilitating or may be adequately treated. Around the world there are other definitions of when a disease becomes rare,  ranging from 1 in 1000 to 1 in 200,000 of the population. But it is agreed that it applies to hundreds of millions throughout the world.
Accepted there are a lot of rare people,  but where can I find a list of all the rare disease conditions.”
There isn’t such a list nor data base of rare diseases not even one containing those where the rarity definition overlaps. There are lists. NORD( National Organisation of Rare Disorders )has a database of 1200 rare diseases * and Orphanet **has a database too but it is not known how many diseases it contains as it lists nearly  22000 diseases including their subtypes . GARD***( Genetic and Rare Diseases) is another which has a database but it overlaps with genetic diseases which are not defined as rare.
Each of them includes aHUS though.
”So aHUS is a rare disease by any of the definitions”
Yes even if it was the 1 in 200 000 of the population definition, that would cover the high end prevalent  aHUS patient population of 5 in  million. But its prevalence is just as likely to be 2 in a million or 0.02 in 10,000 which makes its prevalence very rare.
”Prevalent / Prevalence?”
Yes people who have survived and are living with aHUS today.
“ So there will be between 15000 and 39000 aHUS patients globally”
Exactly that is a good rough estimate. You are getting a handle on  Rare Disease estimating.  Go  one step further , as the Rare Disease community does,  by settling  on a single and more memorable number  e.g. diseases at 7000 and 300 million for people affected,  so let’s say that there are 20,000 aHUS  patients globally.
It is neither wrong nor right but it is more likely that outside of those countries with treatment access those affected will not survive an encounter. So the number of surviving patients is more likely to be towards the lower end of  your estimated range. 20000 is a more memorable number and still a lot of people.
”Yes 20, 000 is still a lot, yet so few that there could be  an accurate record of how many are living with aHUS”
You would think so, but there is not.
aHUS patient frequently ask how many aHUS patients there are in my region , country… the World. It is a topic on their Global aHUS Research Agenda.
But basically it would require patient records to be kept and shared within each country  and for all countries to join together to keep a global registry of numbers  up to date. Even the so called “Global aHUS Registry”, or Alexion Registry, fails to do that as it only includes some aHUS patients in countries in which Alexion sells its drugs. So you can see the problem.
Particularly as aHUS may be different diseases.
“aHUS may not be aHUS!?”
Not quite , it is still aHUS but it may be reclassified into a number of different diseases which result from the hampering of Complement control. Each of them may be  a rare disease in its own right. Some considerably rarer therefore than the ultra rare disease  that is  aHUS .
”The rarest of rare diseases perhaps”

Possibly but not likely. For that they would have to be the one and only. Until a couple of years ago there was a patient with Ribose 5 phosphate isomerase deficiency , or RPI deficiency, who was the one and only recognised patient to have that disease. But in recent years two more patients have been diagnosed as having RPI deficiency.
The rarest rare disease cohort now has a prevalence of 1 in 3.8 billion people  , because  there are only  2 people affected.
Twin sisters Catherine and Kirstie Fields from Llanelli in South Wales in the U.K. have a disease which is named  after them , Fields Disease.

Catherine and Kirstie ( from the newspaper Daily Mail see link below)

Fields is a neuromuscular disorder causing muscular degeneration .There is no treatment only palliative care. The chronic and debilitating disease has left the twins unable to walk and talk. More information can be found about them in this  article in  a newspaper. 
This may not be available in all countries so alternatively “Google”- “Fields Disease” there is even a video that  the sisters made about Fields on YouTube.
“Wow what strength they show in their adversity and  what spirit and by choosing American and Australian accents for their computerised voice systems, what humour they still  display. More should be known about people like them around the world and what needs to done”
It is Rare Disease Day on 29 February 2020.
”Thanks I will support and share the message

Rare is many worldwide

Rare is strong every day

Rare is proud everywhere ”

Note database /lists of rare diseases:
* NORD database
** Orphanet database
*** GARD database
oddly the rarest disease is not listed in any of the above databases as Field’s Disease.
Find out more about what the alliance is planning to do for Rare Disease Day click  below.


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