The mechanisms of itch in psoriasis involve the immune system, the neural system and interactions also with keratinocytes.
There are several mediators that are extremely important in this. Some of it is
cytokines such as interleukin 17, interleukin 23.There’s also interactions
with a non-stem energic neural pathway that includes proteases, substance P and
its receptor neurokinin 1, some ion channels in nerves including TRMP8
which is a receptor for cold and TRMP3. There’s also interactions with some
phospholipids that are overexpressed. So a very important factor called nerve
growth factor that is involved in sensitization of nerve fibers and also
in psoriasis. So the biologics have made a big difference for patients with
psoriasis itch because they reduce it quite rapidly and particularly IL-17
antibodies which reduce itch in 2 weeks time, and it’s very robust. Other drugs that
also can reduce itch are of PD for oral drugs, as well as some of the older
biologics such as TNF inhibitors and IL-12 and IL-23.
However they are less robust in their itch improvement. There is still a lot to
explore.There’s also some areas that are extremely itchy such as scalp itch
psoriasis which is a challenging area to deal with and as a area where most
probably we’ill better understand how the hair follicle and the nerves interact
and better treatments for that would be very helpful for our patients.