Pruritus Flashcards
What are the chemical mediators of itch?
Histamine PGE2 Acetylcholne Serotonin Kallikrien IL 2 Substance P truptase
How is itch transmitted?
Unmyelinated C fibres (different ones transmit itch to those that transmit pain)
What are the CNS mediators of itch?
Opiates (endogenous and exogenous)
List some mast cell degranulation stimuli?
Allergen IgE complex
Substance P
Stem cell factor
C5a
Codeine
IgE direct binding
Anti-FceRI
List the pre-formed mediators released by dermal mast cell degranulation?
Proteases
Heparin
Histamine
List the newly synthesised mediators released by dermal mast cell degranulation?
Prostaglandin D2
Leukotrienes C4, D4, E4
Platelet activating factor
List the four types of itch?
Prupritoceptive
Neuropathic
Neurogenic
Psychogenic
Define pruritoceptive itch?
Something in skin that triggers itch
usually associated with inflammation or dryness
Define neuropathic itch?
Damage of any sort to central or peripheral nerves causing itch
Define neurogenic itch?
No evident damage in CNS but itch caused by e.g. opiate effects on CNS receptors
Define psychogenic itch
Psychological causes with no (currently detectable) CNS damage, e.g. itch in delusions of infestation
What are some systemic diseases associated with itch?
Haematological Paraneoplastic Liver and bile duct Psychogenic Kidney disease Thyroid disease
List some anti-itch treatments?
Sedative anti-histamines
Emollients (with menthol or cooled in fridge)
Antidepressants
Anti-epileptics
Phototherapy
Opiate antagonists
