الفهرس 
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Abstract
Psoriasis is relatively common, chronic, inflammatory and hyperproliferative skin disease that may appear at any age and affect any part of the skin. It affects 1.4 % to 2.0 % of the population and comprises 2.6% of skin related visits to primary care physicians, or between 0.3% and 1.6% of all visits to family physicians. It is a very troublesome disease with a high economic impact.
The disease often persists for life, and the patient has an increased risk of cardiovascular diseases and their complications. One out of five patients develops psoriatic arthritis.
The clinical picture of psoriasis is highly variable with regard to lesional characteristics and the severity of disease.
The characteristic histological features of the disease are epidermal hyperproliferation and infiltration of both dermis and epidermis by inflammatory cells including neutrophils, lymphocytes, macrophages and mast cells. Interactions between infiltrating T cells and skin resident cells (keratinocytes, fibroblasts, endothelial cells) are often mediated by the synthesis and release of different proinflammatory cytokines.
Methotrexate (MTX) can irreversibly bind to dehydrofolate reductase and blocks deoxyribonucleic acid synthesis. It is considered a potential treatment option for rapidly growing cells and exerts an anti-inflammatory effect through inhibition of the polyamine pathway in autoimmune diseases.
General mechanism of action the cytotoxic effect of 5-FU occurs via pathways that adversely affect the normal synthesis and functioning of RNA and DNA (Longley et al., 2013). After entering the cell via the same facilitated transport mechanism as uracil, 5-FU is converted to fluorodeoxyuridine monophosphate (FdUMP), fluorodeoxyuridine triphosphate (FdUTP), and fluorouridine triphosphate (FUTP) by multistep enzymatic reactions.