Pruritis Flashcards
What is the neuropathology of itch?
Sensation is passed through peripheral nerves, up the spinal tract
Itch sensation is processed in parts of the forebears and the hypothalamus
What are some chemical mediators of itch in the skin?
Histamine PGE2 Acetylecholine Serotonin IL-2 Substance P
What element of nerve transmission mediates itch?
Unmyelinated C fibres
What CNS mediators mediate itch?
Opiates
What are the classes of causes of itch?
Pruritoceptice
Neuropathic
Neurogenic
Psychogenic
What is pruritoceptive itch?
A factor, usually associated with inflammation or dryness, within the skin triggers itch
What is neuropathic itch?
Damage to the central or peripheral nerves causes itch
What is neurogenic itch?
No damage to the CNS, but itch is caused by effects on CNS receptors
What is psychogenic itch?
Psychological cause with no (currently detectable) CNS damage
What are examples of pruritoceptive itch?
Insect bite reaction
Lichen planus
Psoriasis
What are some systemic diseases associated with itch?
Haematological Paraneoplastic Liver and bie (e.g. PBC) Kidney damage Thyroid disease Psychogenic
How is itch managed?
Determine cause and treat Anti-histamines Emollients Antidepressants Phototherapy Opiate antagonists
What substances cause mast cells to degranulate?
Allergens IgE Anti-IgE Substance P Stem cell factor C5a Codeine
What mediators are released by mast cell degranulation?
Preformed: protases, heparin, histamine, cytokines
Newly-formed: prostaglandin D2, leukotrienes, platelet-activating factor
