Pathomechanism of Pruritus in Psoriasis and Atopic Dermatitis: Novel Approaches, Similarities and Differences

Abstract

Pruritus is defined as an unpleasant sensation that elicits a desire to scratch. Nearly a third of the world’s population may suffer from pruritus during their lifetime. This symptom is widely observed in numerous inflammatory skin diseases—e.g., approximately 70–90% of patients with psoriasis and almost every patient with atopic dermatitis suffer from pruritus. Although the pathogenesis of atopic dermatitis and psoriasis is different, the complex intricacies between several biochemical mediators, enzymes, and pathways seem to play a crucial role in both conditions. Despite the high prevalence of pruritus in the general population, the pathogenesis of this symptom in various conditions remains elusive. This review aims to summarize current knowledge about the pathogenesis of pruritus in psoriasis and atopic dermatitis. Each molecule involved in the pruritic pathway would merit a separate chapter or even an entire book, however, in the current review we have concentrated on some reports which we found crucial in the understanding of pruritus. However, the pathomechanism of pruritus is an extremely complex and intricate process. Moreover, many of these signaling pathways are currently undergoing detailed analysis or are still unexplained. As a result, it is currently difficult to take an objective view of how far we have come in elucidating the pathogenesis of pruritus in the described diseases. Nevertheless, considerable progress has been made in recent years.

Inhibition of the JAK-STAT Pathway in the Treatment of Psoriasis: A Review of the Literature

“…JAKis seem to have better results in this area than TNF-α inhibitors or apremilast [76,103,104]. This could bring a valuable addition to psoriasis treatment, since for many patients, pruritus is the most bothersome manifestation of the disease [137].…”

Dermatomyositis with Eosinophils

“…Additionally, studies have demonstrated that IL-31 appears to contribute to the induction of pruritus in psoriasis. However, IL-31's relationship with pruritus intensity is not well established [30]. A study by Purzycka-Bohdan et al found substantially elevated levels of IL-31 in psoriasis patients compared to healthy controls, with 97.4% of psoriasis demonstrating pruritus.…”

The involvement of keratinocytes in pruritus of chronic inflammatory dermatosis

“…1 Approximately 70%-90% of psoriasis patients and virtually all AD patients endure relentless itching, which not only exacerbates skin lesions but also affects mood, disrupts sleep patterns and impairs daily functioning. 2 Additionally, a subgroup of individuals with dermatological conditions, particularly those with AD, experience dysesthesia, manifesting as alloknesis (itch triggered by wearing clothes) or hyperknesis (exaggerated itching in response to typically itch-evoking stimuli). 3 Regrettably, pruritus often receives inadequate attention in patient care, despite its substantial burden on society.…”

“…Chronic pruritus is frequently observed in various inflammatory dermatoses, notably conditions such as AD and psoriasis, as well as certain systemic or neurological diseases 1 . Approximately 70%–90% of psoriasis patients and virtually all AD patients endure relentless itching, which not only exacerbates skin lesions but also affects mood, disrupts sleep patterns and impairs daily functioning 2 . Additionally, a subgroup of individuals with dermatological conditions, particularly those with AD, experience dysesthesia, manifesting as alloknesis (itch triggered by wearing clothes) or hyperknesis (exaggerated itching in response to typically itch‐evoking stimuli) 3 .…”