Psoriasis is a little known, chronic, relapsing, immune-mediated, T-lymphocyte-mediated inflammatory disease of the skin in which the “turn over” of keratinocytes is accelerated. Psoriasis is now considered an immune-mediated disease mediated by activated T-lymphocytes, and up to one third of cases may also be accompanied by joint involvement.
More than 125 million people suffer from psoriasis worldwide, a figure which gives an idea of the number of people whose lives are affected by the disease every day. In Spain, approximately 800,000 people suffer from psoriasis.
And research into quality of life in psoriasis reveals a negative effect on patients similar to that observed in diseases such as cancer, diabetes or heart failure. A large number of patients with psoriasis have moderate or severe psoriasis requiring systemic treatments and/or phototherapy for its control.
Today, research has achieved important advances in the field of psoriasis, although there are no treatments that cure, many patients can now live without the discomfort caused by the disease. So-called “biological therapy” (which acts at the level of the etiopathogenic alteration of psoriasis) has brought about a change in both the approach and the management of the patient with psoriasis.
Causes of psoriasis
As we said, psoriasis is a disease whose etiology is not fully understood and in which different factors are involved. On the one hand, there is a genetic predisposition; a percentage of first-degree relatives of a person with psoriasis will also suffer from the disease, while the figure for second-degree relatives is low.
There are also a number of environmental factors that can trigger or worsen a psoriasis outbreak. Among these factors, we find: infections, some drugs (lithium, antimalarials, non-steroidal anti-inflammatory drugs, b-blockers,…), psychogenic factors, climatic factors (heat, cold, sun,…) factors of our own metabolism (calcium, alcohol,…) and endocrine factors, (during puberty and menopause there are peaks of maximum incidence of psoriasis).
In recent years the considerations on the pathogenesis of psoriasis have changed substantially since until the 80’s it was considered that the hyperproliferation of keratinocytes together with the alteration in epidermal differentiation was the primary cause of psoriasis. This criterion was based on the fact that in the psoriasis plaque the keratinocyte cell cycle is reduced by up to eight times compared to the normal cycle and that the number of dividing keratinocytes is doubled.
Various advances in molecular biology and biotechnology have already shown that psoriasis is more of an immunological disease mediated by the activation of T lymphocytes in response to stimulation by an antigen or self-antigen whose nature is unknown. Thus, hyperproliferation and accelerated cell turnover of keratinocytes would be nothing more than the consequence of the stimulation of T-lymphocyte activation.
Epidemiology of psoriasis
A small percentage of the population suffers from psoriasis in the different countries of the world, with the Scandinavian countries having the highest figures. In Asia it is not very prevalent as well as among the American Indian population and people of color. In Spain the population affected by psoriasis affects both sexes equally.
Psoriasis can begin at any age and in fact it has been described in newborns as well as in an elderly man who was diagnosed at 108 years of age. The age of onset also varies from country to country, ranging from 12.5 years in the Faroe Islands to 36 years in Hong Kong. If we focus on Spain, the average age of onset is 29 years, with a certain tendency for it to begin earlier in women than in men (28 years in women and 32 in men). In general, by the age of 30 years a large percentage of patients have started their disease. From a careful analysis of these data it can be deduced that the lower the age of onset in a population, the higher the prevalence, and vice versa.