Derm. Misc. 4 - Pruritus Flashcards Preview

2nd Year - Dermatology > Derm. Misc. 4 - Pruritus > Flashcards

Flashcards in Derm. Misc. 4 - Pruritus Deck (31):
1

What is pruritus?

An unpleasant, poorly localised, non-adapting sensation that provokes the desire to scratch

2

Difference between young and adult scabie mites?

Young mite = 6 legs
Adult = 8 legs

3

Major steps in the mediation of an itch? (4)

Chemical mediators in the skin are released due to mast cell degranulation
This causes nerve transmission through C-fibres
Opiates in the CNS = mediators
Itch sensation is then processed in the forebrain and hypothalamus

4

Examples of chemical pre-formed mediators released by mast cell degranulation? (4)

Proteases
Heparin
Histamine
Cytokines

5

Examples of chemical newly-formed mediators released by mast cell degranulation? (4)

Prostaglandin D2
Leukotrienes C4, D4, E4
Platelet-activating factor
Cytokines

6

Mast cell degranulating stimuli? (8)

Allergen
Anti-FceRI
IgE
anti-IgE
substance P
stem cell factor
C5alpha
codeine

7

What are the names of the 4 causes of an itch?

Pruritoceptive
Neuropathic
Neurogenic
Psychogenic

8

What is a pruritoceptive itch?

something (usually associated with inflammation or dryness) in the skin that triggers the itch

9

What causes a neuropathic itch?

Damage of any sort to central or peripheral nerves causing itch

10

When is an itch classed as neurogenic?

No evident damage in CNS, but itch caused by it e.g. opiate effects on CNS

11

What is a psychogenic itch?

An itch with psychological causes with no (currently detectable) CNS damage

12

Example of a psychogenic itch?

Itch in delusions of infestation

13

What type of itch is a generalised itch due to central effect of endogenous opioids secondary to a small bile duct obstruction?

Pruritoceptive and neurogenic

14

What type of itch is demorgraphism?

Pruritoceptive and neurogenic

15

What is dermographism?

Excessive mast cell degranulation and histamine release caused by stroking the skin

16

What type of itch is asteatotic eczema?

Pruritoceptive

17

What is asteatotic eczema?

Skin is abnormally dry, itchy or cracked = direct exposure of itch-asossicated unmmyelinated C-fribres in bases of micro fissures and inflammation with release of mediators in skin

18

What type of itch is insect bite reactions?

Pruritoceptive

19

What type of itch is lichen planus?

Pruritoceptive

20

What type of itch is psoriasis?

Pruritoceptive

21

What type of itch is prurigo nodularis?

Pruritoceptive

22

What type of itch is MS?

Neuropathic

23

What type of itch is shingles?

Neuropathic

24

What type of itch is caused by drugs such as opiates and tramadol?

Neurogenic

25

What type of itch is caused by haematological conditions e.g. chronic iron deficiency?

Neurogenic

26

What type of itch is caused by paraneoplastic syndrome?

Neurogenic

27

What type of itch is caused by kidney disease?

Neurogenic

28

What type of itch is caused by thyroid disease?

Neurogenic

29

General management of pruritus? (3)

Determine cause if possible
Treat cause if possible
Anti-itch treatments

30

Examples of anti-itch treatments?

Selective anti-histamines (useless for most itch except where excess histamine is part of mechanism)
Emollients (with menthol or cooled in fridge)
Anti-depressants
(for some types of neuropathic itch, anti-epileptics)
Phototherapy
Opiate antagonists
Odansetron (a serotonin antagonist)

31

Anti-depressant useful for some itches

Doxepin