Evaluation of capillary density in psoriasis: An intrapatient study and literature review

Background Dilated and tortuous vessels within elongated dermal papillae represent a histopathological clue of psoriasis. However, the number of dilated capillaries (capillary density) in psoriasis remains undefined as the results from the available studies differ significantly. Objectives To evaluate the capillary density in psoriasis using dermoscopy and horizontal histopathological sections (HHS), two techniques that share the horizontal view of the skin, and to compare the results with the existing data. Methods Twenty adult patients with stable plaque psoriasis were enrolled and, in each patient, a target area of the examined plaque, previously engraved by gently rotating a 5-mm biopsy punch device, underwent dermoscopy and biopsy for HHS. In all examined fields, capillary density was evaluated in a centered 4-mm diameter area, counting the number of red dots at dermoscopy and of dermal papillae at HHS. Results A total of 20 target lesions located on the trunk, arms and tights were evaluated. The mean capillary density resulting from dermoscopy was 43.02 +/- 6.60/mm 2 whereas that from HHS was 50.30 +/- 9.05/mm 2. These data showed a statistically significant difference (p = 0.006), with a strong correlation at Pearson's test (r = 0.88). Conclusions Our results when compared with those from the existing literature showed some differences. The peculiarity of our work is represented by the precise measurement and correlation of the capillary density using two different methods, as the preliminary skin engraving allowed a perfect match between the area undergoing dermoscopy and that of skin sampling for HHS. Compared to dermoscopy in which deep-located vessels might have gone undetected, HHS seems to reflect more precisely and reliably the real capillary density showing an average of 50 capillaries/mm 2 that in a common 5x5 cm psoriatic patch corresponds to an average of 125.000 capillaries. These results highlight the extraordinary potential of psoriatic skin to develop such a complex and intricate vascular network.