Over-expression of tumor necrosis factor-alpha in vitiligo lesions after narrow-band UVB therapy: an immunohistochemical study

There is a growing evidence that cytokines are important in the depigmentation process of vitiligo, however, the exact mechanism is not fully understood. The aim of this work was to study the possible role of the tumor necrosis factor-alpha (TNF-alpha) cytokine in the depigmentation process of the disease. Twenty patients with generalized vitiligo were exposed to narrow-band ultraviolet B (NB-UVB) therapy thrice weekly for a total of 60 sessions. Immunohistochemical examination was done, to assess the TNF-alpha expression in lesional and perilesional skin as compared to normal control skin, before and after therapy. At baseline, positive lesional TNF-alpha expression was detected in 60 \% of patients which was significantly higher as compared to perilesional skin (20 \%) and negative expression in healthy control skin. Post-treatment, a statistically significant increase in TNF-alpha expression was detected in both lesional (90 \%) and perilesional skin (70 \%) as compared to baseline (P < 0.05). The significant increase of TNF-alpha in vitiligo lesions compared with perilesional and healthy skin suggests a possible involvement of this cytokine in the depigmentation of vitiligo. The increase in TNF-alpha expression after NB-UVB phototherapy suggests another role in repigmentation.