Relationship Between the Serum Total Bilirubin and Inflammation in Patients With Psoriasis Vulgaris

Background Psoriasis is a chronic and recurrent inflammatory skin disease. Previous studies have shown that bilirubin has anti‐inflammation and antioxidant effects. However, the various roles of bilirubin in psoriasis patients are still unclear. Objective To investigate the serum total bilirubin (TB) level in the individuals with psoriasis vulgaris and further evaluate the relationship between serum TB concentration and C‐reactive protein (CRP) to clarify the effect of bilirubin on inflammation. Methods A total of 214 patients with psoriasis vulgaris and 165 age‐ and gender‐matched healthy control subjects were recruited. The peripheral leukocyte count (white blood cell, WBC) and differential, serum biochemical and immunologic indexes including serum TB, immunoglobulin (Ig) G, IgA, IgM, complement C3 and C4, as well as serum CRP concentrations were measured. Results Results showed that the serum TB level decreased significantly and peripheral WBC, neutrophil, and serum CRP concentrations increased significantly in patients with psoriasis vulgaris. Meanwhile, the serum CRP was negatively correlated with serum TB levels but positively correlated with peripheral WBC and the Psoriasis Area and Severity Index (PASI). Logistic regression analysis showed that the serum TB was a protective factor for psoriasis vulgaris. Conclusion The present study suggests that lower serum TB is associated with the enhancement of the inflammatory response in psoriasis vulgaris. Therefore, lower serum TB has a prognostic significance for worsening psoriasis vulgaris. Bilirubin may play a crucial role in inflammation by contributing to the inhibition of the inflammatory response.