Part 1 - Patho-Physiology of Pruritus

Hi. With this video [Part 1], we will discuss the physiology of the Itch-Scratch cycle, and the involved mediators and receptors. A good understanding of the itching process is essential to manage this common and troublesome symptom. This video is directed towards dermatologists and is not at all advisory for non-medical personnel.
Introduction - 05:10
Sensory Nerves - 09:50
Stimulus - 11:32
Histamine - 18:31
Other Mediators - 21:23
TRPV1 Receptors - 23:00
H4 Histamine Receptors - 27:48
PAR Receptors - 29:59
Neurokinin Receptors - 32:37
Opioid Receptors - 35:46
Other Receptors - 39:09
Sensory Nerves - 42:24
Cortical Processing of Itch - 47:44
Negative Feedback Mechanisms- 51:00
Definitions - 55:16
Further Reading - 01:00:15
End - 01:00:43
Further Reading:
1. Garibyan L, Rheingold CG, Lerner EA. Understanding the pathophysiology of itch. Dermatol Ther. 2013 Mar-Apr;26(2):84-91. doi: 10.1111/dth.12025. PMID: 23551365; PMCID: PMC3696473.
2. Cevikbas F, Lerner EA. Physiology and Pathophysiology of Itch. Physiol Rev. 2020 Jul 1;100(3):945-982. doi: 10.1152/physrev.00017.2019. Epub 2019 Dec 23. PMID: 31869278; PMCID: PMC7474262.
3. Herndon JH Jr. Itching: the pathophysiology of pruritus. Int J Dermatol. 1975 Sep;14(7):465-84. doi: 10.1111/j.1365-4362.1975.tb04281.x. PMID: 1099034.
4. Martins MS, Almeida IF, Cruz MT, Sousa E. Chronic pruritus: From pathophysiology to drug design. Biochem Pharmacol. 2023 Jun;212:115568. doi: 10.1016/j.bcp.2023.115568. Epub 2023 Apr 26. PMID: 37116666.
5. Fitzpatrick’s textbook of Dermatology. 9ed. Part 2 - Chapter 21: Neurobiology of the Skin, pg - 351
6. Bolognia 4ed, chapter 5: Cutaneous Neurophysiology. Pg - 101

[@pratibhajp2171]

Thanks a lot for this detailed video, it's means alot to dermatologist

[@sabhderma]

My pleasure 😊 glad you found it helpful 😁

[@roshanisk5189]

Sir is there any classes for dermat pg students?

[@ila6136]

Very helpful. Thank you very much. 🙏🏾

[@sabhderma]

Glad it was helpful! 😁😁

[@drjaleena9918]

Thank u

[@sabhderma]

Thanks and keep watching 😀

[@namrathaputtur5964]

Sir please provide pdf for these slides

[@sabhderma]

Hi, I am working on how to share the notes as these ppts have information from various sources. Will let you know when the notes would be available. Till then, keep seeing the videos please 😊😊

[@jinishajain3829]

I had a doubt sir, why does dermarophytoses cause itch where as p. Versicolour is usually non itchy.

[@sabhderma]

That is a very interesting insight. I don't know. But I may suggest that m furfur is a commensal, so maybe the immune cells do not elicit a stronger response to the fungi. While dermatophyte is an exogenous organism with greater immune mediated defense reaction, hence a strong itch response. Itching as a response evolved to rid the body of the pathogens. M furfur is a commensal. So maybe the itch response is not that strong. I hope this makes sense. Thank you for your comments ☺️☺️

[@jamyangchoden1446]

@@sabhderma p versicolor is not itchy because it stays within the stratum corneum where the nerve endings don’t reach

[@sabhderma]

@@jamyangchoden1446 good contribution. But what about dermatophytes that don't cross dej but are still very itchy?

[@jamyangchoden1446]

@@sabhderma unmyelinated C fibres reach up to granular layer of epidermis, maybe that’s why sir?

[@sabhderma]

That is a good contribution. Okay, let's discuss. nerve fibres are found in all layers of the epidermis, so the sensations can come from all layers. P versicolor also penetrates sub-corneal layers in some patients, but is still not itchy. It may even induce a good immune response! While dermatophytes, even with little penetration can be very itchy. I think the reason lies in the host immune response to individual fungal species. P versicolor does not induce a significant immune response, may be they being a commensal and all. Activated immunity releases pruritogens leading to itching. I hope this is a useful explaination. let me know if these helps. Thank you for your comment. I might discuss pathology of itch in dermatophyte infections. it is interesting to understand and read. :) :D