Background Administration of narrow-band ultraviolet B (NB-UVB) is a routine treatment modality for psoriasis, but its effect on human b-defensin 2 (HBD2) level has not been well studied.Aim of the study The aim of the study was to assess immunohistochemically the expression of HBD2 in patients before treatment and compare the results with controls and also assess immunohistochemically the expression of HBD2 in psoriatic lesions before and after NB-UVB phototherapy treatment, thereby assessing the effect of NB-UVB phototherapy treatment on HBD2 expression. Patients and methodsThis study included 30 patients with psoriasis and 30 age-matched and sex-matched controls. HBD2 expression was detected by immunohistochemical analysis in patients before and after NB-UVB treatment. It was also detected in control specimens, which were obtained from excess skin that was removed as a routine during procedures such as abdominoplasty and partial thickness skin grafting in the plastic surgery department.A 50-year-old male patient with a mild Psoriasis Area and Severity Index score of 6.4 before treatment, which reduced to 1.6 after treatment.NB-UVB on the expression of HBD2 Aly et al. 45