Psoriasis : State of the Art 2013 : Part I : Clinical, Historical, Epidemiological and Genetic aspects, Co-Morbidities and Pathogenesis

Psoriasis affects about 2 to 3 % of the caucasian population. It is a chronic inflammatory disease affecting predominantly the skin with the involvement of autoimmune mediated mechanisms. Typical pathogenic features include an increased renewal of epidermal keratinocytes, the enlargement of the germinating compartment, papillomatosis, altered epidermal differentiation, angiogenesis, lymphangiogenesis and inflammatory infiltration. Several types of psoriasis are distinguished and may be present simultaneously in some patients. Up to 20 candidate genes have been evidenced in psoriasis. Genetic variability explains different types of the disease and influences response to therapeutics. Furthermore, psoriasis is triggered or aggravated by infections, traumatisms, medications, stress, tobacco, alcohol and endocrine factors. Severe psoriasis is frequently associated with comorbidities as obesity, diabetes, metabolic syndrome and cardiovascular diseases. For this reason, the similar pathogenic mechanisms of psoriasis and other IMID's (Immune Mediated Inflammatory Diseases) and the use of systemic treatments shared with other specialties, an updated vision of psoriasis for the internist is mandatory