Tissue hemostasis is shifted toward thrombogenesis in the psoriatic plaques.

Background: Psoriasis is a common autoimmune disease of unknown etiology. Recently, much attention has been paid to evidence that a local hypercoagulable state is an important contributing factor to the development of inflammatory skin diseases. Thus, the aim of this study was to characterize the local hemostasis in the affected skin of patients with psoriasis.

Methods: Skin biopsies of psoriatic plaques were obtained from 73 consecutive patients (48M, 25F, average age 45 years) with at least a one year history of the disease. The studied patients had not received any specific systemic treatment for at least 4 weeks before the biopsy was done. As a control, normal skin biopsies were obtained from 16 healthy subjects. For immunohistological study, the En-Vision method (DAKO EnVision Kit ®/Alkaline Phosphatase detection system), and monoclonal antibodies anti-tissue factor (TF), anti-thrombomodulin (TM) and anti-von Willebrand Factor (vWF) were used. All these molecules were assessed semi-quantitatively in the frozen sections.

Results: Clinically, the Body Surface Area index ranged between 1-90% and the Psoriasis Area Severity Index score ranged from 1.6 to 47. Immunohistochemistry revealed redistribution of TF antigens from the upper to lower layers of the epidermis as compared to the control. It was collaborated with the number of TF-positive cells in the psoriatic skin sections (78.3%) as compared with the healthy subjects (34.4%; P<0.001). In addition, TF was uniformly and moderately expressed on capillary endothelial cells of the plaque sections in 43 out of 73 patients (58.9%). As far as the thrombomodulin is concerned, TM was clearly down-regulated and localized mainly in the upper layers of the psoriatic epidermis. It was collaborated with the number of TM positive cells in the psoriatic skin sections (38.9%) as compared with the healthy subjects (66.7%; P<0.001). All capillary vessels found in the biopsy sections were positive for TM and vWF staining, with similar expression (≥2+) in both groups. In the current study, no relationship was found between the TF, TM and vWF expression and the PASI and BAS (NS).

Conclusions: A local procoagulable state found in psoriatic plaques suggests a significant role of local tissue hemostasis in pathogenesis of the disease. These findings indicate another potential target for a therapeutic approach in patients with psoriasis, although further research would help elucidate the exact mechanisms.