Frequently Asked Questions

Histiocytic Disorders and Rare Diseases

Why are all of these diseases with different names considered to be related to each other?
All of the diseases are caused by the over-production of white blood cells called histiocytes. Their different classifications depend on the type of histiocyte involved.

Where can I find reliable information about histiocytosis?
Histiocytosis UK online community provides a number of informational documents and articles, as well as links to medical articles about the histiocytic disorders. While the Internet does provide a significant volume of information about histiocytic disorders, some of this information is not accurate. It is important to look for documents that are current, are free of grammatical and spelling errors, appear to be objective, are free of advertisements, and clearly state their sources.

How can I explain histiocytosis to family and friends?
Histiocytosis is a rare disease that is caused by the over-production of a type of white cell that can lead to organ damage and the formation of tumors. The Histiocytosis UK FAQ pages are also a great way to help explain these complicated diseases to family and friends.

What is Rare Disease?

• A rare disease is defined by the European Union as one that affects less than 5 in 10,000 of the general population.
• There are between 6,000 and 8,000 known rare diseases.
• Around five new rare diseases are described in medical literature each week.
• 1 in 17 people, or 7% of the population, will be affected by a rare disease at some point in their lives.
• This equates to approximately 3.5 million people in the UK and 30 million people across Europe.
• In the UK, a single rare disease may affect up to about 30,000 people.
• The vast majority of rare diseases will affect far fewer than this – some will affect only a handful, or even a single person in the whole of the UK.
• 80% of rare diseases have a genetic component.
• Often rare diseases are chronic and life-threatening.
• Rare diseases can be single gene, multifactorial, chromosomal or non-genetic.
• 75% of rare diseases affect children, and 30% of rare disease patients die before their fifth birthday.

Where can I learn more about rare diseases in general?
Rare Disease UK (RDUK) is the national alliance for people with rare diseases and all who support them. www.raredisease.org.uk.
Orphanet – Database/information about rare diseases with translation available in numerous languages. http://www.ojrd.com
Please be advised that all the information you read here is not a replacement for the advice you will get from your consultant and their team.

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