INTRODUCTION
Psoriasis is a common, chronic, inflammatory, multisystem disease with predominantly skin and joint manifestations, affecting approximately 2- 3% of the worldwide population.1
Disease severity, evaluated by various assessment tools including PASI, BSA, and PGA, drives the therapeutic algorithm as guidelines usually suggest topical medications and phototherapy for mild or mild-to-moderate psoriasis, while for moderate-to-severe or severe psoriasis systemic conventional therapies are prescribed and they include methotrexate (MTX), cyclosporine A (CyA), PUVA, fumarates, acitretin, and biologics.2
Current understanding of the pathophysiology has led to very encouraging developments for the treatment of this disease. The identification of key-mediators, such as tumour necrosis alpha (TNF-α), involved in psoriasis pathogenesis as selective drugable targets, profoundly changed the history of this disorder. These therapeutics are used whether conventional systemic therapies are contraindicated or ineffective. The TNF-α inhibitors, namely adalimumab, etanercept, and infliximab are significantly efficacious in the treatment of both plaque psoriasis and psoriatic arthritis.3-5 Because they do not cause organ toxicity, they may be used as long-term therapy.6,7 Among them, infliximab, which is a human/mouse chimeric anti-TNF-alpha antibody, has been demonstrated effective in ameliorating both psoriatic skin lesions and joint involvement.8
Clinical response induced by TNF-alpha blockade correlates with the reduction of inflammatory biomarkers such as C-reactive protein (CRP) and serum matrix proteinase.9
Although infliximab shows a favourable safety profile, diagnostic blood and imaging tests are mandatory and recommended before starting and during treatment in order to rule out any infection, metabolic or bloodstream alteration, and malignant tumor.10
Protein electrophoresis is part of the blood test panel used to evaluate any eventual change in the serum protein profile. Alterations such as monoclonal gammopathy of undetermined significance (MGUS) may be detected in patients undergoing treatment with biologic agents.11-14 In accordance with previous