Background: The etiology of psoriasis, one of the most common chronic dermatoses, has not been elucidated yet. Involvement of antioxidant enzymes is suspected. The study aimed to determine the
concentrations of lipid peroxidation products reactive with thiobarbituric acid and antioxidant enzymes activity.
Material/Methods: 67 patients of the Chair and Clinic of Dermatology (22 females and 45 males) with psoriasis vulgaris of 3 to 34 years’ duration were examined. All were treated topically with preparations
for external use. Smooth skin was treated with salicyl ointment, cignoline and tar, while salicyl oil and betamethasone dipropionide with salicylic acid was used on the scalp. Lipid peroxidation
products reactive with TBA, expressed as malondialdehyde (MDA) concentration, were determined in erythrocytes using Buege and Aust method. Activities of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), were determined in erythrocytes according
to Misra and Fridovich, and Beers and Sizer, respectively.
Results: In healthy subjects, SOD and CAT activity was 1049.2±261.9 U/gHb and 41.4±13.7 × 104 IU/gHb, respectively, and MDA concentration 35.8±10.5 nM/gHb. MDA concentrations in erythrocytes
of psoriatic patients before treatment were 44% higher and SOD and CAT activities 20% and 27% lower, respectively, than those observed in the controls. Topical treatment improved the patients’ clinical condition, resulting in slow increase of enzyme activity to values comparable with controls.
Conclusions: The results confirm the involvement of antioxidant enzymes in the pathogenesis of psoriasis. It is, however, questionable whether the observed abnormalities are responsible for the onset
of psoriasis, or resultant from ongoing pathologic process.

Keywords: Catalase - metabolism, Erythrocytes - metabolism, Lipid Peroxidation, Malondialdehyde - metabolism, Ointments - therapeutic use, Psoriasis - drug therapy, Psoriasis - metabolism, Reactive Oxygen Species - metabolism, Superoxide Dismutase - metabolism, Thiobarbiturates - metabolism