## 4 Discussion
from the AI model versus subjective measurements of the ET was 13.5%, which is, with respect to the aforementioned reasons, very good. In scans with greater undulation of the stratum corneum or wavy DEJ, the AI-supported measurements seem to calculate smaller but also more exact results because of computing a mean over the whole stack. In conclusion, the main difference between both methods, which also represents a limitation of the study, lies in the fact that subjective measurements were confined to a representative area, whereas the AI model calculated an average across the entire scanned part of the lesion. Future studies could potentially address this discrepancy by manually measuring multiple psoriasis areas and calculating a mean, which might yield results more comparable to those obtained by the AI. Moreover, the statistical insignificance of DEJ undulation reduction (\(p\) = 0.148) observed in this study may be attributed to several factors inherent to the study design and patient population. First, the relatively small sample size (12 patients) limits the statistical power necessary to detect subtle changes in DEJ undulation. Additionally, the heterogeneity of the treatment regimens, with patients receiving different biologic therapies (secukinumab, izekizumab, and bimekizumab), and variability in the anatomical location of the psoriatic plaques (lower and upper extremities, including the scapular region) may have introduced variability in treatment response. The variation in age (25 to 84 years; mean: 52.9 years), and differences in baseline DEJ characteristics across patients might also contribute to the lack of statistical significance. Moreover, the study duration (median of 5.4 weeks between V0 and V1, and of 8.1 weeks between V1 and V2) might have been insufficient to capture more profound changes in DEJ undulation. The persistence of elongated rete ridges and other dermato-epidermal alterations, which could diminish at a slower rate compared to hyperkeratosis and acanthosis, may have contributed to the observed results. Another consideration is the technical limitations of LC-OCT; undulation changes might be more challenging to quantify with this imaging modality, as it relies on averaging across the entire lesion, potentially underestimating localized variations. In future studies, increasing the sample size, standardizing treatment regimens, and extending the follow-up period might help provide more definitive insights into the significance of DEJ undulation changes under therapy. Additionally, integrating imaging modalities with greater penetration depth, such as dynamic OCT, could enhance the sensitivity of detecting subtle alterations in the DEJ. In concordance with the results obtained by [PERSON]\(\ddot{\text{s}}\)sing, [PERSON] [37], inflammatory cells in the epidermis were also present in most of our patients in the SP. During the study, when the dermis became visible in most patients, inflammatory cells could also be detected in this skin layer in the majority of cases. Interestingly, bright inflammatory cells also occurred frequently in the CoA in the epidermis and dermis and persisted in most patients during the study period. This might be a sign of systemic inflammation caused by severe psoriasis. In some patients we also found further psoriatic changes in the CoA, like dilated vessels. Vascular changes at the edge of PP have already been detected by laser Doppler flowmetry as a marker for activity, preceding epidermal alterations and without histologically detectable psoriatic skin alterations [38]. They are thought to be the last psoriatic change persisting in a regressing plaque [39]. Vascular alterations have also been shown to be detectable by videocapillaroscopy in clinically improved or healed skin in PP under therapy with cyclosporine A [40]. In our study, the persistence of dilated vessels could be detected in the majority of patients and also initially in the majority of clinically healthy CoAs.