1. CAUSES OF DISEASE Flashcards
Define aetiology
- Aetiology refers to the cause of a disease or the set of causes
- Diseases can have a single cause or be the product of multiple factors
Define idiopathic
- Idiopathic conditions are conditions that have no KNOWN cause
- They have a cause but the cause is not identifiable
What are the two types of causes for disease?
- Intrinsic - from within
2. Extrinsic - from outside
What does intrinsic mean in regards to disease?
- Intrinsic causes are considered to be changes to an individual’s genome such as:
- Nuclear or mitochondrial, inherited mutations, de novo mutations or epigenetic mechanisms
- These changes result in altered function of a gene or a group of genes which will then cause varying amounts of protein & activity
What are the two ways in which intrinsic causes of disease can manifest?
- Cell autonomously
2. Cell non-autonomously
What is cell autonomy?
- Cell autonomously means that only the cell with the mutation is affected
- The cell with the mutated genotype will display the mutated phenotype
- E.g Cell X has a mutation so it doesn’t secrete the structural protein Y meaning Cell X is the wrong shape
What is cell non-autonomy?
- Cell non-autonomy means that other cells will be affected as a result of the mutation in one cell
- The cell with the mutated genotype will cause other cells to present with the mutated phenotype
- E.g Cell X has a mutation & it doesn’t secrete protein hormone Y so Cell Z is non-functional
What’s the difference between cell-autonomy & cell non-autonomy?
- Cell autonomy = primary effect, only that cell affected
- Cell non-autonomy = secondary effect other cells affected
What does extrinsic mean in regards to disease?
- From outside
- External or environmental factors causing disease
Give 6 examples of extrinsic causes of disease
- There are many extrinsic causes of disease
1. Injury
2. Infection
3. Lifestyle
4. Chemical poisoning (acute or chronic)
5. Nutrition & diet
6. Exposure to radiation
Describe age as a contributing factor to disease?
- Age is not thought to be a cause for disease but is a contributing factor to disease
- Age refers to time
- As time progresses, risk factors accumulate or worsen resulting in disease
How can age be considered an intrinsic cause of disease?
- The biological process of ageing can be considered an intrinsic cause
- Age –> Menopause –> Decrease in oestrogen –> Osteoporosis
Explain why the terms intrinsic & extrinsic are ambiguous?
- It can be difficult to determine whether the cause of a disease is intrinsic or extrinsic because we don’t know the direction of the causal relationship
- E.g asthma can have a intrinsic cause - sensitive immune system or an extrinsic cause - preceding allergen
- So a cause can be classified as intrinsic or extrinsic based on context such as extrinsic to the body, organ, tissue, cell etc.
What are the alternative descriptions of intrinsic & extrinsic?
- Intrinsic = genetic
- Extrinsic = environmental
- Sometimes genetic or environmental is used instead of intrinsic & extrinsic because it’s more reflective of the disease such as Parkinson’s disease.
What is the cause of Down Syndrome & classify it as intrinsic or extrinsic?
- Trisomy of Chromosome 21 - inherited at conception
- Intrinsic cause
