Objective: The objective of this study is to investigate the association between Vitamin D level and psoriasis, in particular in our city of the long, hot, and sunny weather, in an attempt to add a clarification to this controversial subject. Methods: A case–control study included 120 patients with psoriasis and 38 patients with psoriatic arthritis (PsA); 89 (56.3%) patients were male. Psoriasis area and severity index (PASI) was calculated for all patients with psoriasis and disease activity

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... ore using 28 joints (DAS28) and erythrocyte sedimentation rate (DAS28) was measured for all patients with PsA. The control group comprised 164 age- and sex-matched participants (91 males and 73 females). Vitamin D serum level was performed for both patients and controls. Results: Vitamin D levels in both patients and controls were 17.4±7.7 and 28.3±5.6, respectively. The level of Vitamin D was lower in a patient with disease duration equal and more than 10 years than those with a disease duration <10 years. There is no significant difference in Vitamin D levels between the two patient subgroups. Lower Vitamin D levels were associated with high PASI and high DAS28 in psoriasis and PsA, respectively. Conclusion: Patients with psoriasis and PsA associated with low levels of serum Vitamin D. Vitamin D deficiency was found to be associated with long disease duration in both psoriasis and PsA. Patients with active disease have lower Vitamin D levels.