Influence of narrowband ultraviolet B phototherapy on serum tumour necrosis factor-like weak inducer of apoptosis (TWEAK) in patients with psoriasis.

Psoriasis is characterized by keratinocyte resistance to apoptosis. We recently demonstrated an increase in serum tumour necrosis factor-like weak inducer of apoptosis (TWEAK) in patients after topical treatment for psoriasis. We decided to verify whether narrowband ultraviolet B (NB-UVB) has a similar effect. Serum concentration of TWEAK was estimated in patients with exacerbated plaque psoriasis treated with NB-UVB. Baseline TWEAK levels were similar in patients with psoriasis and healthy controls, and Psoriasis Area and Severity Index (PASI) correlated inversely with TWEAK levels. Treatment with NB-UVB caused a significant reduction in PASI and concurrent increase in serum TWEAK. This finding may be due to increased expression of TWEAK receptor in psoriatic skin, which has been reported previously, with consequent binding of excess soluble TWEAK during treatment and subsequent release after treatment. Severity of plaque psoriasis and its improvement after NB-UVB treatment may be associated with TWEAK concentrations. The importance of our findings remains to be established.