الفهرس 
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Abstract
An association between vitiligo and oxidative stress has long been postulated. Decreased catalase, increased malondialdehyde were reported in vitiligo patients. Vitiligo is autoimmune disease in which antibodies, multiple chemokines and cytokines are elevated. In vitiligo, tyrosinase expression which is important for normal pigmentation is decreased by downregulation of cyclic AMP.
Adenosine deaminase is an enzyme involved in purine metabolism and is essential for lymphocyte development, survival and function. ADA induces oxidative stress, increases ROS by decreasing adenosine level and converting it to inosine. Adenosine suppresses production of ROS by neutrophils. ADA increases the secretion of multiple cytokines from mature dendritic cell. ADA affects melanogensis through downregulation of cyclic AMP that leads to decrease tyrosinase expression.
This study aimed to assess ADA in vitiligo patients and compare its level with healthy controls. This study was conducted on sixty patients suffering from vitiligo and twenty apparently healthy individuals as a control. All patients were selected from the Outpatient Clinic of Dermatology Department, Benha University Hospitals in the period from June 2020 to August 2021. The study was approved by the Local Ethics Committee on Research involving human subjects of Benha Faculty of Medicine. An informed consent was obtained from each individual before being enrolled in the study.
Vitiligo patients with other autoimmune diseases, history of active malignancy or taking immunosuppressive treatment, history of systemic treatment of vitiligo for less than three months before the study were excluded. All participants were subjected to complete history taking and general examination to exclude systemic diseases. Vitiligo severity was classified according to VETI score. Serum blood samples were taken from all participants to measure serum tADA with the available ELISA commercial kits according to manufactures’ instructions.
The study revealed the following results
• Serum tADA was significantly higher in patients than controls.
• Serum tADA was significantly higher in generalized than focal vitiligo, unstable than stable vitiligo and those with positive history of treatment than those without.
• Serum tADA showed a significant positive correlation with VETI score, but it showed non-significant correlations with patients’ age and disease duration.
• Serum tADA showed non-significant relations with gender and positive family history.
• ROC curve analysis showed a role of tADA in differentiating between vitiligo patients and controls.
• Serum tADA was a significant independent predictor for vitiligo after controlling of the effect of patients’ age and gender.
Conclusion
The results of this study showed that tADA serum levels were higher in vitiligo patients compared to controls, which may play a role in the pathogenesis of the disease. This study may provide important clues to assist the development of new therapeutic strategies for vitiligo patients.