Serum interferon-gamma is a psoriasis severity and prognostic marker.

The aim of this study was to measure serum interferon-gamma (IFN-gamma) levels in participants with different types and severities of psoriasis. The study was conducted on 21 participants with psoriasis. Participants were divided into 3 groups according to disease severity: erythrodermic, severe plaque, and mild to moderate plaque psoriasis. Fifteen participants received different treatment modalities for 16 weeks and were followed for an additional 12 weeks. The enzyme-linked immunosorbent assay technique was used to measure serum IFN-gamma levels in participants before treatment and compared with matched controls and participants receiving treatment. Significant differences were detected between participants and controls in mean serum IFN-gamma levels before treatment (P<.05). There was a positive correlation between serum IFN-gamma levels and psoriasis area and severity index (PASI) scores, and between serum IFN-gamm levels and clinical type of psoriasis, with the highest serum IFN-gamma levels in the erythrodermic psoriasis group and the lowest in the mild to moderate plaque psoriasis group. Irrespective of the type of treatment, 13 of 15 participants who showed improvement in disease condition with a significant decrease in PASI scores also had a significant decrease in serum IFN-gamma levels (P < .05). Moreover, participants with serum IFN-gamma levels that did not dramatically decrease had a shorter remission period compared with those who showed a significant decrease in serum IFN-gamma levels. The substantial elevation and variation in serum IFN-gamma levels according to disease severity suggest that IFN-gamma has a role in determining disease severity and therapy evaluation, which encourages further research on anti-IFN-gamma biologic therapy in the treatment of psoriasis.