What is Psoriasis?
Lime scab – chronic dermatosis, characterized by frequent relapses, the characteristics of which are skin rashes in the form of scaly papules. This is one of the most common skin diseases that can begin at any age. The course of psoriasis is long and persistent. With remissions of several months or years, the disease continues until the end of life. In exceptional cases, there is a spontaneous cure.
Pathogenesis during Psoriasis
Psoriasis is a systemic process that is formed in patients not only with immune disorders, but also with pronounced morphological and functional changes in various organs and systems. Psoriasis is one of the most studied dermatoses. However, none of the existing hypotheses of psoriasis does not fully reveal the essence of the disease. However, the problems of treatment and prevention of this dermatosis face dermatologists as acutely as many years ago. At various times, various theories of the origin of psoriasis have been proposed. The following forms were highlighted:
- infectious (including viral)
Each of these theories is based on relevant clinical observations and the results of some laboratory tests. Infectious theory is one of the oldest theories of the origin of scaly lichen. At the end of the XIX century. there were known cases of extensive psoriatic lesions after acute febrile conditions such as influenza, scarlet fever. The systemic nature of the lesion, a long relapsing course, the connection of exacerbations with fluctuations of meteorological and heliophysical factors, some features of the evolution of psoriatic lesions, testified in favor of the infectious nature of the disease. Often, researchers have found a link between the relapse of the disease and the exacerbation of foci of focal infection.
It was assumed the relationship of psoriasis with syphilitic and tuberculosis infection. Some researchers believed that the microorganisms found by them in patients with psoriasis are the causative agents of this dermatosis. However, none of these theories could not withstand criticism. At the present time, the participation of various microorganisms in the development of psoriasis as inducers and modifiers of cellular and humoral reactions in the body is being actively discussed.
- The hereditary theory is psoriasis in representatives of 2-5-6 generations, family cases of the disease.
- The exchange theory is a violation of fat (cholesterol) metabolism, an elevated content of phosphorus, DNA and RNA in psoriatic scales, enzymopathies, a decrease in the incidence of disease during famine.
- Viral Theory. The concept of the role of viral infection in the etiology of psoriasis arose on the basis of clinical observations. As far back as 1940, in a number of studies, scientists discovered peculiar acidophilic bodies called “elementary bodies”, which were located intra and extracellularly in the tissue fluid of psoriatic papules. In an experiment on guinea pigs and rabbits after they were “infected” with psoriatic material, the researchers managed to reproduce the morphological changes in the visceral organs in the form of fibrosis, degenerative changes and atrophy of parenchymal cellular elements. Currently, the search continues for viral agents capable of causing the development of the psoriatic process. When examining children with psoriasis using the polymerase chain reaction method, they found human papillomaviruses (HPV5 and HPV36b) in them. Thus, despite the complexity of the problem and the inconsistency of experimental data, from the current point of view there is reason to assume the viral nature of psoriasis. However, for the final confirmation of this theory, it is necessary to isolate and identify the virus.
- Endocrine and exchange theories had in their time numerous supporters. In patients with psoriasis, various endocrine disorders have often been identified, which has led some researchers to explain the etiology and pathogenesis of this dermatosis from the perspective of endocrine theory. There were violations of the functional state of the gonads, the effects of the menstrual cycle, pregnancy, childbirth, the lactation period on the course of the disease, and also found marked changes in the pituitary-adrenal system in patients.
- Neurogenic theory – the onset of the disease after a nervous shock. About 31% of patients associate the exacerbation of psoriasis with stress. Thus, in this category of patients, a significant decrease in the ability to resist stress and cope with their consequences was noted, and the existing asthenic, astheno-depressive, vegetative-vascular-dystonic and vegetative-vascular-visceral disorders with neurotic reactions in such patients contribute to the formation or aggravate the existing vicious circle.
Smoking also adversely affects the course of psoriasis. Associations of the disease with smoking in women have been established, as well as an increased risk of exacerbation of psoriasis in smoking men who have fallen into extreme situations. Alcohol causes an immune imbalance and induces changes in the capillaries of the skin, but the intimate mechanisms of the effect of ethanol on the epidermis in psoriasis are not fully understood. Cases of the occurrence or exacerbation of psoriasis after taking certain medications are described: terbi-nafina, captopril, anabolic steroid hormones, α- and β-interferons. More often than others, antibiotics (26%) caused exacerbation of psoriasis: tetracycline, penicillin, bicillin, chloramphenicol; nonsteroidal anti-inflammatory drugs (15%): butadione, ibuprofen, indomethacin, etc .; B vitamins (15%): thiamine bromide (B1), pyridoxine hydrochloride (B6), cyanocobalamin (B12); delagil, various cytostatics, vaccines, serums, β-blockers (13%). Psoriasis is often exacerbated or manifests (manifested) after taking β-blockers. In HIV-infected patients, a more severe course of psoriasis, characterized by frequent exacerbations, was observed. At the same time, the mechanisms of the provoking action of HIV infection in patients with psoriasis are not fully disclosed.
In psoriasis, under the influence of a hypothetical factor, a deep imbalance is formed in all parts of the cellular and humoral immunity. Changes in the immune system can lead to the involvement of a number of endogenous, in particular leukocyte antigens, in the formation of immune complexes in patients with psoriasis. In turn, immune complexes can directly damage tissues and, moreover, stimulate many humoral and cellular systems of the body, which is accompanied by excessive production of biologically active substances that are also involved in the defeat of the epidermis, thus closing the formed vicious circle in the chain of autoimmune reactions.
In addition to immunological, non-immune mechanisms may also be involved in the pathogenesis (developmental mechanism) of psoriasis. However, none of these theories makes it possible to explain all cases of psoriasis. According to modern concepts, the main role in the development of psoriasis is played by hereditary factors. The so-called latent (hidden) psoriasis is inherited. By this definition is meant a genetically determined predisposition, which is manifested in disorders of cellular metabolism, in particular, in changes in the exchange of nucleic acids in the epidermis. Modification of metabolic processes (metabolism) is observed in both affected and clinically and histologically healthy skin, not only in patients with psoriasis, but also in healthy family members. The result of the interaction of hereditary and provoking factors is the acceleration of reproduction and the lack of maturation of cells in the epidermis (pathological acceleration), as well as circulatory disturbance occurring in the papillary dermis.
In typical cases, based on the presence of a triad of psoriatic phenomena, on the clinical characteristics of lesions. In the differential diagnostic relation, erythroderma presents great difficulties, especially when it occurs in children. In adults, it is most difficult to diagnose psoriatic lesions of the oral mucosa.