rare_diseases.Rmd

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title: "Understanding Rare Diseases"
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## What Are Rare Diseases?

- A rare disease affects fewer than 1 in 2,000 people.
- Over 7,000 rare diseases exist.
- 80% are genetic
- 70% of rare diseases start in childhood.

> While individually rare, together they affect 3.5-5.9% of people worldwide.
> In [Africa](https://doi.org/10.1186/s13023-022-02391-w), there is a lack of reliable data on how many people are affected, but it is estimated to be around **50 million**. That's around 1 in 25 Africans!


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## The Diagnostic Odyssey

Patients often have to go through:
- Years of unanswered questions
- Seeing multiple specialists
- Having countless, sometimes unnecessary, tests
- A lack of treatment or support even after a diagnosis

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## How Are Genetic Conditions Inherited?

- **Single Gene Conditions** – Caused by changes in one gene  
- **Chromosome Conditions** – Caused by missing or extra chromosomes  
- **Multifactorial Conditions** – Involve many genes and the environment

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## Types of Inheritance

### Dominant

- One changed gene copy is enough
- 50% chance of passing to each child

### Recessive

- Two changed copies are needed
- Parents are usually carriers

### X-linked

- Mutations on the X chromosome
- Affects males more often

![](https://rareshareprod.s3.amazonaws.com/uploads/ckeditor/pictures/50/content_DomRessive.png)