Vitiligo is acquired depigmentation disorder. Several theories were hypothesized for causing vitiligo, of which the autoimmune theory is the most accepted.~The main targets of therapy are stabilization of the disease activity through immunosuppression, and repigmentation through stimulation of reservoir melanocytes proliferation and migration.~Narrow band ultraviolet phototherapy (NB-UVB) remains the cornerstone treatment of vitiligo. NB-UVB can induce both immunosuppression and repigmentation. Several factors can modulate the efficacy of NB-UVB therapy in treatment of vitiligo cases, including patient's age, lesion site, duration of the disease, and duration of the therapy.~The immunosuppressive function of NB-UVB was first detected in 1963 by Hanisko and Suskind, who observed that the contact hypersensitivity response in skin sensitized to dinitrochlorobenzene (DNCB) was reduced if skin was previously exposed to suberythemal doses of UVB.~Present evidence suggests that UVB suppress immune system through generation of T-suppressor cells, which inhibit the effector cells of Th1 type. It appears that UV-induced immunosuppression depresses the function of Th1 cells and enhances the activity of Th2 cells via cytokines such as Interleukin 10.~It's expected that this immunsupression is lower in darker skin types, where increased basal melanin might act as a barrier. However, skin was previously divided to UVB-resistant and UVB-sensitive (UVB-R and UVB-S) based on the contact hypersensitivity testing, regardless of the skin type. Moreover, A study on NB-UVB phototherapy for psoriasis revealed that photoadaptation during NB-UVB therapy Is Independent of skin type.
Vitiligo is a disease in which autoimmunity plays a major role. Multiple treatment options are available, of which narrow-band UVB is a cornerstone, acting through immunosuppression and repigmentation by stimulating reservoir melanocytes.~It's expected that this immunsupression is lower in darker skin types, where increased basal melanin might act as a barrier.