What is psoriasis?

Although psoriasis has been known since ancient times (the term psoriasis derives in fact from the Greek word for “scale”), it was defined and recognized as a distinct pathological entity only in 1841, by Ferdinand von Hebra; since then, much information has been acquired about this disease of great social importance, for its spread in the population and for its impact on the quality of life of the patient.

Psoriasis is an inflammatory dermatosis of a chronic-recidivating nature, characterized by typical erythematous-desquamatory lesions localized, in the classical forms, at the level of the extensory surfaces of elbows and knees, of the sacral region and of the scalp; in reality today it is correct to classify the disease as a real syndrome constituted by subgroups with very different clinical-evolutionary characteristics; in the severe forms, moreover, it is highly invalidating because it limits the social and working life of the affected subject. The doctor must therefore pay particular attention in assessing the patient, taking into account not only the skin organ, but also any joint localization or the concomitance of other diseases, as well as the psycho-emotional experience of the subject, the approach must be basically multidisciplinary and systemic.

The estimated prevalence of disease is around 2-3% of the world population, and it is estimated that currently there are about 130 million people with psoriasis in the world (in Italy alone there are 2 million). Of these, about a quarter suffer from forms of medium to severe severity, such as to require systemic therapies; in a percentage of cases between 5 and 42%, psoriasis is associated with a particular form of inflammatory arthritis, precisely called psoriatic arthritis. As far as the age of the first onset of manifestations is concerned, there are two peaks of onset, an early one, between 16 and 22 years old, and a later one, between 57 and 60 years old; it is above all subjects with familiarity with psoriasis who show a tendency towards an earlier onset (often with more serious manifestations) of the disease.

Causes of Psoriasis

Not all the causes that lead to the onset of the disease are known, but there are many heritable genetic factors that contribute to the appearance of clinical manifestations, which are sometimes triggered by external factors such as infections (especially streptococcal pharyngo-tonsillar infections and perianal skin, related to a form of psoriasis), The disease is also known as guttata, a characteristic of the paediatric age), emotional stress, climate change (typically the disease worsens or worsens in the winter months and improves, until it disappears, in the summer months with exposure to sunlight), pregnancy, hormonal factors (hypocalcemia), surgery or trauma (scratches, burns, scars); in the latter case, due to the phenomenon of Koebner (or reactive isomorphism), psoriatic lesions may appear on intact skin at the site of trauma, after 1-2 weeks. Various drugs, including lithium salts, blockers, ACE inhibitors, synthetic tetracyclines and antimalarial drugs, can also induce or aggravate the disease, and finally it is necessary to take into account the habits of life that potentially expose to the risk of disease, in particular diet, alcohol and cigarette consumption.

Whatever the risk factors and agents capable of triggering the disease, what is now clear is that they act by triggering an abnormal immune reaction that manifests itself clinically with psoriatic lesions and whose activation is objectively appreciable through the histological observation of the patches: psoriasis is therefore an immunomediated dermatosis due to extremely complex mechanisms, whose operation involves multiple cell types and in which cytokines and soluble factors have the role of regulatory purposes.

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