6: Mechanisms of pruritus Flashcards

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1
Q

What is pruritus?

A

Unpleasant, poorly localised sensation that makes you want to scratch

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2
Q

What is a possible advantage of pruritus and subsequent scratching?

A

Removal of parasites e.g scabies

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3
Q

Which parts of the brain are thought to be responsible for pruritus?

A

Forebrain

Hypothalamus

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4
Q

Name a chemical mediator for pruritus.

A

Histamine

amongst many others

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5
Q

Apart from histamine, what other types of signal can trigger pruritus?

A

Nerve transmission

CNS mediators (i.e opiates)

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6
Q

Which immune cells contain histamine and are triggered to degranulate by IgE (in complexes with allergens) and IgG?

A

Mast cells

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7
Q

Apart from histamine, what else do mast cells contain?

A

Heparin

Proteases

Prostaglandins

Leukotrienes

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8
Q

Which immune cells look similar to mast cells and share some of the same functions?

A

Basophils

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9
Q

What are the four general causes of itch?

A

Pruritoceptive

Neuropathic

Neurogenic

Psychogenic

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10
Q

What causes a pruritoceptive itch?

A

Something pathogenic in the skin e.g inflammation / dryness

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11
Q

What causes a neuropathic itch?

A

Damage to central or peripheral nerves

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12
Q

What causes a neurogenic itch?

A

CNS mediators e.g opiates

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13
Q

What causes a psychogenic itch?

A

Psychological issues e.g delusions of infestations

CRAWLING IN MY SKIIIIN

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14
Q

What is dermographism?

A

Minor stroking causes mast cell degranulation and an inflammatory rash

also known as skin writing”

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15
Q

What is asteatotic eczema?

Where is it usually found?

What type of pruritus is it associated with?

A

Eczema due to dry skin

Shins

Pruritoceptive

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16
Q

Give two examples of pruritoceptive itches.

A

Asteatotic eczema

Insect bites

Dermographism

Lichen planus

17
Q

Give two GI diseases which cause a neurogenic itch.

A

Primary biliary cirrhosis

Chronic hepatitis

18
Q

What is the first thing that should be done in the treatment of pruritus?

A

Treat the underlying cause if you know what it is

19
Q

What are some non-specific therapies a patient can try to resolve their pruritus?

A

Antihistamines

Emollients

Antidepressants

Phototherapy

Opiate antagonists