Psoriasis is a chronic immune-mediated disorder affecting about 2% of the population worldwide which is associated with significant morbidity. The disease usually presents as raised, well-demarcated erythematous plaques with adherent silvery scales. Psoriasis can appear at any age but it has two peaks occurring at 15–20 and 55–60 years of age. It affects males and females equally. Despite the multitude of investigations about psoriasis and even development of drugs with satisfactory results, its pathogenesis is not fully understood yet and its course is unpredictable. Various environmental triggers, e.g., obesity, stress and drugs may induce disease in genetically susceptible patients. Although psoriasis was considered primarily as a disease of the skin, more investigations have been revealed its systemic nature. Psoriatic arthritis (PsA) may complicate up to one-third of cases of psoriasis vulgaris (PV). Also, the association between psoriasis and a variety of other immune-mediated disorders such as inflammatory bowel disease (IBD) and celiac disease (CD) has been confirmed in various studies. Moreover, a growing body of evidences indicates that psoriasis shares some common histological and phenotypical properties with the spectrum of osteoimmunological diseases such as Paget’s disease of bone (PDB). Thus, exploring the common molecular and genetic mechanisms underlying psoriasis and related disorders is of paramount importance for better elucidating disease pathogenesis and designing more targeted treatments.

There is an increasing need for appropriate effective treatment and long-term disease control in patients with psoriasis because of the decreased quality of life, increased physicosocial deficits and associated co-morbidities. Systemic conventional treatments that are the first step in the management of moderate-to-severe plaque psoriasis include methotrexate (MTX), acitretin, cyclosporine and fumarates. MTX is considered the gold standard in the treatment of moderate-to-severe chronic plaque type psoriasis. It is also used to treat pustular psoriasis, erythrodermic psoriasis and psoriatic arthritis. Acitretin monotherapy is less effective than other conventional systemic treatments for plaque psoriasis, while superior to generalized, palmoplantar pustular, and hyperkeratotic variants. Cyclosporine is preferred in the presence of unstable acute clinical conditions (erythrodermic or generalized pustular psoriasis) and also in induction phase of rotational and sequential therapy for severe resistant psoriasis, due to its rapid effect. Dimethyl fumarate, which has similar efficacy to MTX, is an appropriate option in the induction and long-term systemic treatment for adult patients with moderate to severe plaque psoriasis without psoriatic arthritis. Although they are often overshadowed by biologics at the stage of preference by most physicians and patients today, they are classical and inexpensive agents with known long-term results. When the appropriate patient profile and psoriasis type are selected at the right time and necessary laboratory and clinical follow-ups are made, each of them is an effective treatment with reliable and satisfactory results. In this article, important points (recommendations according to patient characteristics, psoriasis type and comorbidities) to be considered in clinical practice when using the conventional anti-psoriatic agents in the treatment of psoriasis are overviewed.