Phototherapy decreases red blood cell deformability in patients with psoriasis.

Background: Alternations in erythrocyte deformability (ED), namley, the ability of erythrocytes to change shape under flow in the microcirculation, can contribute to cardiovascular diseases. Psoriasis, a systemic inflammatory skin disorder, is associated with an increased cardiovascular risk. The effect of psoriasis and psoriasis treatment on ED was only scarcely evaluated.

Objective: To evaluate ED changes in psoriasis patients following narrow band-ultraviolet B (NB-UVB) treatment.

Methods: Erythrocyte deformability was determined using a computerized cell flow properties analyzer in 9 patients with psoriasis before and after a course of Goeckerman regimen. ED was quantified using two parameters: average elongation ratio (AER) in the cell population, and the fraction of low deformable cells (% LDFC).

Results: All 9 patients showed decreased ED (i.e. impaired deformability) following NB-UVB treatment. There was a significant (p = 0.003) decrease in AER after treatment (AER±SD; 1.58±0.06) compared to the starting values (1.69±0.1). Additionally, there was a significant (p = 0.002) increase in the fraction of low deformable cells (% LDFC±SD; 60.00±9.05) compared to their fraction before treatment (34.86±11.44).

Conclusions: The decreased ED observed following phototherapy could have clinical influences on psoriasis patients, and may partially explain why phototherapy does not decrease the cardiovascular risk in psoriasis compared to other treatments.