## 4 Discussion  
Pruritus defined as an unpleasant sensation that provokes a desire to scratch was observed in 93% of all patients in our study. In other research, this phenomenon was reported with a frequency of 63-98% [14; 15; 16; 17; 18; 19]. These differences may be due to regional features, the clinical characteristics of patients, and the divergent study methodologies used in other centers. To date, pruritus in psoriasis has already been investigated several times, but researchers have not distinguished any clinical subtypes of psoriasis or have mainly been focused on plaque-type psoriasis [20; 21; 22]. However, psoriasis manifests with several morphological phenotypes that may differ regarding the intensity and perception of pruritus. In the literature, descriptions of both prevalence and the clinical characteristics of pruritus in psoriasis are limited and contradictory [23; 24; 25]. Here, we have presented the results of a multicenter, prospective study analyzing pruritus in various morphological subtypes of psoriasis. In our study, there was no relationship between the subtypes of psoriasis and the frequency of pruritus. Compatible results were observed by [PERSON] with his group, albeit assessment was performed only in guttate and plaque subtypes [16]. Similarly, [PERSON] et al., [PERSON] et al., and [PERSON] et al. found that the presence of itch did not depend on the type of psoriasis, although the number of considered clinical subtypes were limited [18; 26; 27]. In contrast, another research team noticed some differences in the prevalence of pruritus. The most pruritogenic variant according to [PERSON] et al. was palmoplantar psoriasis, whereas the least pruritogenic was guttate psoriasis (67.6% and 50.0%, respectively) [14]. On the other hand, two other studies suggested that the presence of pruritus was mostly linked to the pustular subtype [28; 29]. Regarding localization of pruritus, we paid attention to whether pruritus was limited to lesional skin or also concerned uninvolved skin. In most psoriasis variants, pruritus was limited to psoriatic lesions. Contrarily, in one previously conducted study, itch was not limited to involved areas [18]. These divergent results may be caused by several limitations of [PERSON]'s trial: smaller studied group (\(n=101\)), only three differentiated subtypes (plaque, guttate, erythrodermic), and 45% of subjects receiving antihistamines [18]. In our study, the only exception was erythrodermic psoriasis, in which generalized pruritus was more prevalent. However, it can be easily explained by specific skin involvement in erythrodermic psoriasis, which affects more than 80% of the skin [30]. The data on the interplay between psoriasis severity and itch remains inconclusive-some investigators have shown a positive connection between these factors, while others reported a lack of correlation [6; 18; 29; 31]. However, even if the analysis was based on some different subtypes of psoriasis, the severity of the disease was assessed collectively [18; 27]. In our groups of examined patients, we observed that the intensity of pruritus increased along with disease severity, but statistical significance was confirmed only in some disease variants. The most prominent relationship was found between the intensity of pruritus and the severity of the scalp psoriasis and PPPP. In nummurl psoriasis, only the 10-PPS score correlated positively with psoriasis severity. However, such correlation was not significant according to the NRS\({}_{\text{max}}\) and NRS\({}_{\text{average}}\) scores. This result can be explained by the complex and multifactorial assessment of pruritus in the 10-PPS scale, which allowed for a more detailed evaluation of the intensity of pruritus along with the extension, duration, and the influence of pruritus on concentration, psyche, and scratching. Furthermore, in GPP, the extension of skin lesion measured by BSA was linked to higher pruritus intensity.