UNPAR PATOFISIOLOGI GATAL

7/23/2019 UNPAR PATOFISIOLOGI GATAL

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ITCH

PATHOPHYSIOLOGY

Ninik Sukartini

Clinical Pathology Dept. FMUI



INTRODUCTION

• Itch is the principal symptomof sin !isease an! is an

important sin manifestationof systemic !isease"

• Ho# !oes scratchin$temporarily relie%e itch &



introduction

• Classifcation o itch : – Pr'ritocepti%e : generated in the skin usually

y an in!a""atory or other #isile pathologicalprocess eg scaies$ urticaria

– Ne'ro$enic : generated in the CNS in responseto circulating pruritogens as in cholestasis

– Ne'ropathic : due to anato"ical lesions o thecentral or peripheral ner#ous syste"s eg ner#e

entrap"ent$ tu"our – Psycho$enic : including delusional parasitosis



Itch receptors

• %pider"is &especially keratinocytes'constitute the itch receptor

• (eratinocytes e)press a range o

ne'ropepti!e me!iators and receptors *hich in#ol#ed in pruritus

• Mediators : opioids$ ner#e gro*th actor&N+F'$ sustance P

• ,eceptors: #anilloid receptors$ proteinaseacti#ated receptor type - &P,-'$ #oltage/gated 0P channel



Neural path*ay or itch

• Slo#(con!'ctin$ 'nmyelinate! C ne'rons *hich only trans"it itch &and te"peraturechanges' in response to hista"ine

• ,epresent only aout 1 2 o total neurons

• Selecti#ely acti#ated in the chronic pruriticskin disease

• Contralateral transmission ne'rons$

consist o an itch/specifc suclass o la"ina 3spinothala"ic tract neurons$ con#ey itch tothe thala"us





,egulation o itch• Inhi)itory ne'ronal circ'it located in the

sustantia gelatinosa o the posterior horns ospinal cord a $ate! mechanism *hereya4erent itch can e regulated

• Increased tone in descending path*ay results

ro" #isual$ auditory and other sti"uli acti#ation o inhiitory neuronal circuit closureo the gated "echanis" di"inished itch tra5c

reason !'rin$ !aytime* itch is less

tro')lesome• ,esult o an i"alance et*een opioid actions

on central 6 &increasing itch' and κ &di"inishingitch' receptors





Mediators o itch

• Cross(tal )et#een C ne'ron terminals an!the spatially closely relate! !ermal mast

cells

• 7ista"ine

%icosanoids ligates 73 receptors associated

0NF/8 *ith C neuron

• 0ryptase acti#ate P,- e)pressed on a4erent

C neuron ter"inals

sti"ulates itch sensation9 triggers release o sustance P urther"ast cell acti#ation





Mediators o itch

• Ne'rotrophins +NG,- causesprolieration o un"yelinateda4erent ner#e ter"inals$

sensitisation o a4erent ner#eter"inals and increased e)pressiono neuropeptides

• (eratinocytes e)press high le#el oN+F

• 7igh urinary and plas"a le#el o N+F

ound in patient *ith atopic ece"a



Ho# !oes scratchin$ temporarily relie%e itch &

• Scratching acti#ates thickly

"yelinated ast/conducting ;neurons *idespread surroundinhiition to acti#ation o theInhi)itory ne'ronal circ'it



Itch o cholestasis

• <pioids cause intense pruritus

• =iliary ostruction leads to increasedintrahepatic synthesis o opioidpeptides *hich spill o#er in to thecirculation and cause pruritus yacting on 6/opioid receptors in

central ner#ous syste"



Than yo'

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UNPAR PATOFISIOLOGI GATAL