Rare diseases are diseases which affect a small number of people compared to the general population and specific issues are raised in relation to their rarity. A disease can be rare in one region, but common in another. 1
While nearly all genetic diseases are rare diseases, not all rare diseases are genetic diseases. There are also very rare forms of infectious diseases, such as auto-immune diseases and rare cancers. To date, the cause remains unknown for many rare diseases. There are thousands of rare diseases.1-2
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