Pruritus

Question 1

What is pruritus?

Answer 1

Itch

Question 2

What are some mediators of pruritus?

Answer 2

Histamine, PGE2, ACh, unmyelinated C fibres, opiates.

Question 3

What are the 4 causes of pruritus?

Answer 3

Pruritoceptive, Neuropathic, Neurogenic, Psyhogenic

Question 4

What is a pruritoceptive cause?

Answer 4

Something in the skin that triggers an itch. Normal stimuli.

Question 5

What is a neuropathic cause?

Answer 5

Damage to nerves causing them to sense itch without stimuli.

Question 6

What is a neurogenic cause?

Answer 6

CNS generates itch sensation usually due to stimuli on it such as opiates.

Question 7

What is a psychogenic cause?

Answer 7

Itch completely psychologically derived- delusion of infestation etc.

Question 8

Is psoriasis itchy?

Answer 8

Almost always but less than eczema.

Question 9

What is prurigo nodularis?

Answer 9

Lesions caused by scratching chronic itch.

Question 10

Give some causes of neurogenic itch.

Answer 10

Haematological- Fe2+ deficiency.
Paraneoplastic
Liver/biliary tree- Bilirubin etc
Psychogenic
Kidney disease- Due to an inability to filter our opioids
Thyroid disease

Question 11

How should you treat itch?

Answer 11

Determine cause
Treat cause
Give anti-itch treatments:
-Sedative anti-histamines
-Emollients
-Antidepressents 
-Phototherapy
Opiate antagonist