Study of serum levels and skin expression of S100B protein in psoriasis*

BACKGROUND S100B protein was reported to be elevated in psoriatic patients' serum, with no previous evaluation of its skin expression, in contrast to the extensively studied S100 protein. OBJECTIVE To evaluate the serum level and skin expression of S100B in psoriasis to assess its possible involvement in its pathogenesis. METHODS Serum level of S100B protein was estimated in 40 psoriatic patients of different clinical varieties and 10 healthy controls. S100B protein expression was assessed immunohistochemically in lesional and non-lesional skin of patients and in normal skin of controls. Relation to disease severity was also evaluated. RESULTS Serum level of S100B protein was significantly higher in psoriatic patients (0.15±0.03 µg/l) than in controls (0.03±0.007 µg/l) (P-value <0.001) with no significant correlation with PASI score. On comparing grades of S100B protein skin expression in lesional and non-lesional skin biopsies, a statistically significant difference was found (P=0.046) with higher percentage of strong S100B skin expression (60%) in non-lesional than in lesional (42%) skin. All the control biopsies showed negative expression. STUDY LIMITATIONS Relatively small sample size with a limited range of low PASI scores. CONCLUSION This study points to a potential link between psoriasis and S100B protein with higher serum and skin expression in patients than in controls.