Causes of disease: overview

Question 1

What is the term for a condition with no known cause?

Answer 1

idiopathic

Question 2

What are the causes of disease organised into?

Answer 2

Causes of disease are usually categorized as intrinsic or extrinsic
• Intrinsic = from within
• Extrinsic = from outside

Question 3

What can cause intrinsic disease?

Answer 3

= Changes in an individual’s genome
• Nuclear or mitochondrial
• Inherited mutations and other genetic variations
• de novo mutations
• Epigenetic modifications
Typically alter the function of a gene (or group of genes)
• E.g. more/less protein or same amount but more/less activity
Effects of genetic variations can manifest at a variety of levels
• Cell autonomously
o Cell X no longer expresses structural protein Y, so cell X is the wrong shape
• Cell non-autonomously
o Cell X no longer secretes protein hormone Y, so cell Z no longer functions

Question 4

What can cause extrinsic disease?

Answer 4

Numerous including:
•	Injury
•	Infection
•	Nutrition and diet
•	Lifestyle, e.g. smoking, exposure to workplace toxins
•	Chemical poisoning (acute and chronic)
•	Exposure to radiation

Question 5

How are the terms intrinsic and extrinsic ambigous?

Answer 5

• Causes of disease are often a chain of events
o Are allergies caused by a sensitive immune system (intrinsic) or the preceding allergen (extrinsic)?
• Intrinsic or extrinsic depends on viewpoint,
i.e. extrinsic to what: cell, tissue, organ, body?

Question 6

Does age cause disease?

Answer 6

• Age is a contributing factor to many diseases, but is it a cause?
• Age really just means ‘time’, in the context of causes that accumulate, e.g.

Question 7

Give alternative descriptions of disease

give an example

Answer 7

1. For many diseases, causes are grouped as “genetic” and “environmental”
2. These terms are versions of intrinsic and extrinsic that are more reflective of that disease

on image