Introduction

Psoriasis is a model disease in dermatology. It is a common disease that affects at least 2 to 3% of the population in the European Union. As a matter of fact, more than half of patients do not take care of themselves, either because the inefficacy of the treatments available discourages them or because such treatments strike them as being more restrictive than psoriasis itself, or because they are in remission.

It is an illness only present in humans, characterized by an excessive reaction of the skin to attacks from the internal and external environment, most often of genetic origin. These attacks can be immunologic, mechanic, metabolic, drug-induced or psychological. As such, understanding the physiopathology of psoriasis calls for a greater understanding of the interactions between the skin cells on the one hand and the interactions between the skin and the central nervous system (CNS) on the other. This excessive reaction is characterized by epidermal proliferation combined with incomplete terminal differentiation, as well as an excessive inflammatory response responsible for the chronic nature of the lesions. The way to understand psoriasis is to reach therefore a better appreciation of the messages that enable the skin cells to initiate an inflammatory response, and a better understanding of the way in which the inflammatory cells, responsible for innate and acquired immune responses, are capable of bringing about proliferation and abnormal epidermal differentiation. Taking an interest in psoriasis is thus taking an interest in all facets of skin physiology and in all the ways the skin reacts to environmental aggressions.

[|Organisation of
psoriasis care differs between countries. It is important to plan psoriasis care
together with the patient associations. Psoriasis day care centres have become
increasingly common, especially in Scandinavia
in recent years.|auteur193]

For over thirty years now, more than 300 publications endeavour to explore each year one aspect or another of psoriasis from a clinical, epidemiological, physiopathological or therapeutic point of view. There is no new technique for observing the skin that has not been immediately applied to the study of psoriasis—which is a privileged mirror of the progresses made in dermatology. Nor has psoriasis remained untouched by whims of fashion, all kind of scenarios having been suggested to explain it, from a scarring disease to an autoimmune illness, or even a genetic or psychosomatic disorder.

Psoriasis is at the origin of a medical revolution necessary to complete and enhance the effectiveness of evidence-based medicine; it is the so-called “patient-based medicine”. This concept refers to the development of techniques aiming to apply the scientific evidence-based medicine knowledge, built by studying populations, to an individual and specific patient.

Psoriasis is very rarely life threatening. Conversely, it is a disease that does affect, sometimes very severely, the quality of life. The patient is the judge of his or her quality of life, and it is, therefore, up to the patient, not to the doctor, to gauge the severity of psoriasis. This is a key point to decide the best therapeutic strategy. Psoriasis cannot be treated then without placing the patient, not the illness, at the centre of therapeutic negotiations. The 20th century has witnessed boundless efforts concentrating in the disease; the 21st century witnesses the development of medical techniques that allow the patient, in all its complexity, to be placed at the centre of therapeutic efforts. This revolution began in dermatology, revolving around psoriasis, and is spreading progressively to all chronic disorders and all disciplines.

It is difficult not to be passionate about psoriasis and those suffering from it. The aim of this book is to convey the passion of different experts on psoriasis in the world. The chosen strategy has been to ask experts in the world to react to this position paper. This way we hope to avoid the two scourges of therapy, recipes and one-way thought, by complementing and relativizing each chapter with the views of different experts. Above all, the goal of this book is to initiate a dialogue with the reader.

Professor Louis DUBERTRET