Photoplethysmography in Cutaneous Lupus Erythematosus

Introduction
Cutaneous lupus erythematosus is a chronic inflammatory autoimmune disease of multifactorial etiology. In every form of cutaneous lupus erythematosus, there is a risk of progression to systemic lupus erythematosus at any stage of the disease. Its development is influenced by genetic predisposition, environmental factors and immune system interactions leading to endothelial damage. Photoplethysmography is a non-invasive diagnostic method enabling the assessment of vascular perfusion in distal areas. While its application in cardiology, pulmonology, and neurology is well established, only a few reports have addressed its usefulness in systemic lupus erythematosus, and no reliable studies have documented photoplethysmographic changes in patients with cutaneous lupus erythematosus.

Objective
To evaluate the usefulness of photoplethysmography in patients with cutaneous lupus erythematosus, taking into account the form of the disease, its severity, and its activity.

Material and methods
70 patients with lupus erythematosus (56 women and 14 men) and twenty healthy adults (15 women and 5 men) underwent photoplethysmography using the Rheoscreen Medis device with a light function. The examination was performed on all fingers of both hands. The shape of the photoplethysmographic waves and the intensity of changes observed during the examination were analyzed.

Results
Patients with systemic lupus erythematosus showed significantly more pronounced abnormalities than patients with cutaneous lupus erythematosus (p = 0.010) and those with chronic cutaneous lupus erythematosus (p = 0.001). The severity of abnormalities was also greater in patients with subacute cutaneous lupus erythematosus compared to those with chronic cutaneous lupus erythematosus (p = 0.030) and the control group (p = 0.005). However, no correlation was found between photoplethysmographic parameters and disease activity in either systemic or cutaneous forms of lupus erythematosus.

Conclusions
Photoplethysmography as a method enabling the assessment of microcirculation can be useful in the diagnosis of lupus erythematosus at the stage of cutaneous lupus erythematosus in the course of systemic disease and isolated cutaneous lupus erythematosus form.