Pruritus

Question 1

Define pruritus

Answer 1

An unpleasant sensation that causes the want to scratch

Question 2

What are the two different classifications of pruritus?

Answer 2

• Pruriceptive pruritus= due to stimulation of peripheral receptors in the skin. Usually due to sin disease
• Neuropathic pruritus= generated in the CNS e.g. syringomyelia

Question 3

What nerves/ receptors are involved in the itch response?

Answer 3

• Nociceptors
• Mainly unmyelinated slow conducting C fibres
• Also some A delta fibres

Question 4

Describe the neural pathway for itching

Answer 4

-Sensory afferent signal from skin-> dorsal root to spinal cord-> dorsal horn-> travel up lateral spinothalamic tract -> thalamus-> sensory cortex

Question 5

Describe mediators of pruritus

Answer 5

• Pro inflammatory mediators are released
• Can either stimulate release of more pro inflam, have a direct pruritogenic effect or stimulate mast cells to release pruritogens

Question 6

What is the action of IL-31?

Answer 6

• Binds to receptors on skin surface
• activates JAK enzymes
• stimulates pruritic nerve impulse
• Has associations with allergic skin disease

Question 7

Describe the therapeutic interventions for pruritus

Answer 7

• Corticosteroids= reduce inflammation

- Antihistamines= block H1 receptor on C neurons