Increased urine neopterin levels in psoriasis.

The production of neopterin closely reflects activation of T-lymphocyte-mediated immunity. Oxidized and reduced forms of urine neopterin were measured by reversed-phase ion-pair high-performance liquid chromatography in patients with moderate to severe chronic plaque psoriasis (n = 40), and in a heterogeneous group of patients (n = 14) with cutaneous T-cell malignancies (CTCM). Results were compared with healthy non-psoriatic control subjects (n = 30). Neopterin levels were repeated after a course of ultraviolet B therapy (UVB) plus topical tar or dithranol, or photochemotherapy (PUVA), in 12 psoriatic patients. Fully oxidized urine neopterin levels and neopterin/creatinine ratios were significantly elevated in the psoriatic group compared with controls (P < 0.002, P < 0.05) but not in the CTCM group. Both neopterin and its creatinine ratio were significantly reduced by treatment (P < 0.05, P < 0.01). Psoriasis area and severity index scores (PASI) correlated strongly with urine neopterin levels (P < 0.001). These findings indicate that urine neopterin concentrations may be a marker of psoriatic disease activity, and further support the importance of activated T lymphocytes in the pathogenesis of psoriasis.