الفهرس 
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Abstract
Summary and conclusion
Vitiligo, a common idiopathic acquired depigmentation disorder, occurs mostly among young people, with a 0.5% to 5% incidence worldwide, without sex or skin color predilection. The clinical presentation is characterized by solitary or multiple depigmented macules or patches that may arise in a localized, segmental or generalized distribution. Vitiligo causes cosmetic, psychologic and social problems especially in colored people.
The pathogenic mechanisms in vitiligo have not been completely clarified, although important clues have been found in recent years, there are many theories for the pathogenesis of vitiligo as genetic, autoimmune, neurogenic and autocytotoxic theories.
The aim of this study is to examine the antioxidant defense enzymes GPX and CAT in vitiligo patients and their correlation with the disease activity.
This study was carried out on 30 vitiligo patients and 10 control subjects. Vitiligo patients must not had any treatment for the disease for at least 3 months before the study. Eleven patients in this study showed disease activity at the time of sampling while the remaining 19 had stationary disease.
- Patients were subjected to the following :-
* Complete history taking.
* Dermatological examination.
* Sampling : heparinized blood samples for estimation of
blood GPX activity level.
* Biopsies : full thickness skin biopsies from both normal
skin and vitiliginous skin for estimation of CAT
enzyme activity.
This study revealed the following results:
- There is a non significant decrease in the blood GPX in vitiligo patients compared to its value in control subjects.
- Decreased CAT enzyme activity in skin biopsies taken from vitiliginous skin and normal skin of vitiligo patients in comparison to its activity in skin biopsies from control subjects.
- Normal skin CAT activities showed a significant decrease in patients ≥ 60 years old compared to patients < 60 years. Moreover, vitiliginous skin CAT showed a significant decrease in patients ≥ 60 years old compared to those < 60 years old.
- Significant decrease of tissue CAT and GPX in patients showed disease activity compared to those with stationary disease.
- Significant decrease in the levels of both tissue CAT and blood GPX in diabetic patients with vitiligo compared to non diabetic patients and controls.
The significant decrease in tissue CAT in vitiligo patients could be a good indicator to the ability of ROS in inducing melanocytes dysfunction.
The non significant decrease in blood GPX has been agreed with the results of some studies and disagreed with others. These contradictory results minimize the association between vitiligo and systemic oxidative stress.
The significant decrease of tissue CAT and blood GPX activities in active vitiligo may be related to increased melanocyte sensitivity to oxidative stress in patients with active vitiligo.
Diabetes mellitus is a disease with abnormal metabolism that cause generation of excess ROS. There is significant decrease in CAT and GPX in diabetic vitiligo patients compard to non diabetics. The concomitant abnormalities in expression of antioxidant enzymes in diabetes and vitiligo may enhance the oxidative injury in cases with both diseases.
The decrease in the normal skin CAT activity after age of 60 years may indicate that antioxidant capacity of the body is decreased by this age.
In conclusion, ROS plays a role in the pathogenesis of vitiligo either by increased production or by decreased activity of antioxidant enzymes.
Our observations may lead to the conclusion that enzymatic depletion of tissue CAT provides further support for a free radical mediated damage in vitiligo and that correction of the epidermal redox status is mandatory for repigmentation. Nevertheless, our results were obtained in a small number of patients and further studies are needed for confirmation.