El-Hamd MA, et al. - In patients with acne vulgaris, authors evaluated the serum levels of 25 hydroxy vitamin D and its association with acne vulgaris severity and how levels were impacted before and after treatment with isotretinoin. Before treatment, there was a significant inverse relationship between the level of 25 hydroxy vitamin D and severity of acne vulgaris, and serum levels of 25 hydroxy vitamin D were significantly higher after isotretinoin treatment. Findings suggested a potential role of vitamin D in the pathogenesis of acne vulgaris or acne vulgaris could have a negative effect on vitamin D synthesis.