A visible and progressive improvement in the symptoms of PP over 1 month induction therapy was observed in patients receiving secukinumab treatment (Fig. 1). A total of 100 untreated psoriatic plaques localized on the trunk (46), upper (34), and lower (20) extremities were assessed using RCM. The RCM criteria for psoriasis were based on the histological criteria to diagnose PP. We evaluated the RCM features of the 100 target PP lesions: parakeratosis, acanthosis, epidermal inflammatory cells, non-edge dermal papillae (DP), vascularization in the papillary dermis, and inflammatory cells in the upper dermis (Fig. 2). Two experienced RCM specialists independently analyzed all quantifiable RCM findings to ensure the reliability of the results. The parameters examined by the RCM are presented in Table 1.
Table 1
Confocal features and their definitions
RCM features
|
Definition
|
Parakeratosis
|
The presence of nucleated cells in the stratum corneum is visualized as bright nuclei in dark corneocytes.
|
Acanthosis
(epidermal thickness)
|
Evaluated using VivaStack software analysis considering all cellulated layers until the total appearance of the dermal fibers.
|
Inflammatory cells in the epidermis
|
The presence of bright, round-to-polygonal cells in the epidermis.
|
Non-edge DP
|
Presence of dark dermal papillae more enlarged, not surrounded by bright ring of basal keratinocytes, and adjacent to each other, separated by a thin septum with a coarse fibrillary material.
|
Vascularization in the papillary dermis
|
Round-to-canalicular dark structures with thin walls, inside the DP with multilocular appearance, at the level of the papillary dermis.
|
Inflammatory cells in the dermis
|
The presence of bright or mildly refractive, round-to-polygonal cells around blood vessels in the dermis.
|
This difference in the RCM results across all time points can easily be observed using RCM. RCM Vivablock of PP reveals more prominent and diffusely distributed papillomatosis with enlarged dermal papillae increased in number and density as a sign of elongation of the rete ridges and hyperkeratosis (Fig. 2a). At baseline, 32% of the lesions exhibited parakeratosis, visualized as the retention of bright nuclei in dark corneocytes (Fig. 2b). Its modification during the therapeutic follow-up was statistically significant; nearly no lesions presented parakeratosis after two weeks (T2)(Fig. 2c-d). Acanthosis of the epidermis was evaluated using Vertical Viva Stack software analysis, starting from the upper part of the epidermis immediately below the stratum corneum to the DEJ and considering the entire thickness of the cell layers. Acanthosis was observed in all lesionsat baseline, the mean thickness of epidermis was 94.47 ± 21.27 µm. Although the thickness of the stratum corneum was reduced at T2 (78.46 ± 13.17 µm), the difference was insignificant between T4 and T5 (Table 2). Parakeratosis and acanthosis summarize the epidermal involvement in PP and illustrate the treatment’s impact on restoring normal epidermal proliferation.
Table 2
Friedman test for the evaluation of the statistical significance of the scores related to the groups of confocal criteria defined in Fig. 3 in relation to the response to treatment. Wilcoxon test for pair comparison in relation to the timing of observation
|
Parakeratosis
|
Inflammatory cells in epidermis
|
Non-edge dermal papillae
|
Inflammatory cells in dermis
|
Vascularization in the papillary dermis
|
Achantosis
|
Friedman
test (χ2)
|
P = 0.0004
(22.74)
|
P < 0.0001
(35.29)
|
P < 0.0001
(45.62)
|
P < 0.0001
(48.82)
|
P < 0.0001
(189.0)
|
P < 0.0001
(151.8)
|
Wilcoxon test
|
T1 vs. T0
|
P = 0.0469
|
P = 0.0078
|
P = 0.0039
|
P = 0.0020
|
P < 0.0001
|
P = 0.0004
|
T2 vs. T0
|
P = 0.0313
|
P = 0.0039
|
P = 0.0020
|
P = 0.0020
|
P < 0.0001
|
P < 0.0001
|
T3 vs. T0
|
P = 0.0313
|
P = 0.0039
|
P = 0.0020
|
P = 0.0020
|
P < 0.0001
|
P < 0.0001
|
T4 vs. T0
|
P = 0.0313
|
P = 0.0039
|
P = 0.0020
|
P = 0.0020
|
P < 0.0001
|
P < 0.0001
|
T5 vs. T0
|
P = 0.0313
|
P = 0.0039
|
P = 0.0020
|
P = 0.0020
|
P < 0.0001
|
P < 0.0001
|
T2 vs. T1
|
P > 0.999
|
P = 0.6250
|
P = 0.0078
|
P = 0.0039
|
P < 0.0001
|
P = 0.0005
|
T3 vs. T2
|
P > 0.999
|
P = 0.5000
|
P = 0.0156
|
P = 0.0039
|
P = 0.0004
|
P < 0.0001
|
T4 vs. T3
|
NA*
|
NA
|
P = 0.5000
|
P = 0.0078
|
P = 0.0183
|
P = 0.0010
|
T5 vs. T4
|
NA
|
NA
|
P = 0.5000
|
P = 0.500
|
P = 0.1185
|
P = 0.9248
|
* NA: not available
|
Neutrophils play a well-documented role in the pathophysiology of psoriasis. Pathognomonic neutrophil collections are frequently identified as clusters of highly refractile round to polygonal cells at the stratum spinosum and stratum corneum, where they form micropustules of Kogoj and microabscesses of Munro, respectively. Highly refractile nucleated cells, consistent with neutrophils, were found in 45% of the lesions at T0 (Fig. 2b). During treatment, the considerable reduction in epidermal focal microabscesses could be easily distinguished morphologically by RCM.
In psoriasis lesions, RCM virtual horizontal sections at the level of the DEJ exhibited numerous conspicuous DP with a multilocular appearance. One of the main RCM features observed at the DEJ was the presence of a non-edge DP. Unlike the DP of healthy skin, they were well-defined, more enlarged, adjacent to each other, not surrounded by any bright ring of basal cells. Instead, they were separated by a thin, slightly refractile septum (Fig. 2e). DP in psoriasis may be due to the inhibitory effect of interleukin-17A on melanogenesis. The recovery of DEJ bright rimming, considered as a signal of melanocyte re-activation, has been independently examined. A significant number of lesions (83%) exhibited non-edge DP at baseline; however, DP rimming became statistically significant during treatment between T0 and T1 and T0 and T2 (Fig. 2f-h) (Table 2). A reasonably robust and positive correlation was observed between the variation in DP rimming and the progression in the PASI score from the baseline to T5 (Table 3).
Table 3
Correlation analysis of confocal criteria defined in Fig. 3 and PASI score
|
Parakeratosis
|
Inflammatory cells in epidermis
|
Non-edge dermal papillae
|
Inflammatorycells in dermis
|
Vascularization in the papillary dermis
|
Achantosis
|
Correlation
|
0.422
|
0.548
|
0.796
|
0.829
|
0.825
|
0.793
|
Sig.
(2-tailed)
|
P = 0.001
|
P < 0.001
|
P < 0.001
|
P < 0.001
|
P < 0.001
|
P < 0.001
|
Distributions are represented in the main diagonal and correlation coefficients in corresponding graphs. Data is represented together with a 95% density ellipse and a least squares regression line with a 95% confidence region.
|
PP pathophysiology includes vascularization in the papillary dermis, which was successfully identified on RCM virtual sections as enlarged DP presented multilocular appearance (Fig. 2i). The capillary vessels to become dilated, describing multiple loops in their trajectory, and visible as prominent dark canalicular structures, dilated, and tortuose, filling the papillary dermis throughout the DP rings in 100% of the lesions (Fig. 2j). Micromorphological analysis using the VivaScan 7.0 Software revealed that the mean values of the capillary loop diameter were significantly higher in PP lesions compared to normal skin. Figure 3 summarizes the parameter changes in the capillary loops determined by RCM at all time points. The mean diameter of the capillary loops was 46.59 ± 19.26 µm at baseline in the lesions at T0. Conversely, the dilated and tortuose canalicular structures were not detectable in the patient’s normal-appearing skin (at least 5 cm from the lesion site). The diameter of blood vessels was considerably reduced at T1 (36.36 ± 15.9 µm) and T2 (22.86 ± 4.88 µm) compared with baseline. The difference was statistically significant (P < 0.0001).
Despite the presence of a weak but positive association between vascularization in the DP and the PASI score and minimal papillary blood flow at T3, dilated blood vessels in the DP persisted until T5 (Fig. 2l). A transition in the orientation of the blood vessels was also observed during the treatment. At baseline, PP lesions exhibited vertically oriented blood vessels filling the DP because of up-migrated DP. Enlarged DP presented multilocular appearance, canalicular or round dark spaces represent vessels that run perpendicular to the surface. During treatment, the orientation of the blood vessels was converted; dilated blood vessels (started at T2) showed horizontal orientation and linear formations in the upper dermis (Fig. 2k, l), corresponding to a parallel (en face) orientation to the skin surface.
The rapid movement of numerous prominent, highly refractive polymorphonuclear leukocytes in dark capillary lumen, and presence of mildly refractive monocytes surrounding the dilated vessels in the papillary dermis was identified in all lesions (Fig. 2m). Conventional histology has confirmed that these cells correspond to perivascular inflammatory cell infiltration. A significant decrease in dermal inflammatory cells was observed because of the treatment response compared with the baseline. Dermal inflammatory cells persisted in T5 (Fig. 2n-p), but the reduction was statistically significant.
The PASI score showed progressive global clinical improvement in all patients enrolled in the research. These RCM criteria were compared with the clinical scale evaluation and PASI scores, and the outcomes were statistically significant during follow-up (table. 2).