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Psoriasis: causes, symptoms, treatment
Medical expert of the article
Last reviewed: 05.07.2025
Psoriasis (synonym: pityriasis versicolor) is an inflammatory disease that most often appears as sharply demarcated erythematous papules or plaques covered with silvery scales. What causes psoriasis is unknown, but common causes include injury, infection, and use of certain medications.
Subjective symptoms of psoriasis are usually minimal, with occasional mild itching, but the lesions can be cosmetically problematic. Some patients develop painful arthritis. The diagnosis of psoriasis is based on the appearance and location of the lesions. Treatments for psoriasis include emollients, vitamin D analogues, retinoids, tar, glucocorticoids, phototherapy, and in severe cases, methotrexate, retinoids, biologics, or immunosuppressants.
Psoriasis is a chronically recurring disease, which is based on increased proliferation and impaired differentiation of epidermal cells. The disease lasts for years, accompanied by alternating relapses and remissions.
Psoriasis is a chronic inflammatory dermatosis of multifactorial genesis, in which the genetic component plays a leading role. Psoriasis is characterized by a pronounced spectrum of clinical manifestations: from single, abundantly scaly papules or plaques of pinkish-red color to erythroderma, psoriatic atropia, generalized or limited pustular psoriasis. The rash can be located on any part of the skin, but most often - on the extensor surface of the limbs, scalp, trunk. Psoriatic papules are diverse in their size, intensity of the inflammatory reaction, infiltration, which can be very significant and accompanied by papillomatous and warty growths.
Psoriasis affects about 2% of the world's population, men and women - approximately equally.
[ What causes psoriasis?
Psoriasis is a hyperproliferation of epidermal keratinocytes, accompanied by inflammation of the epidermis and dermis. The disease affects approximately 1-5% of the world's population, with people with fair skin at increased risk. The age-related onset of the disease has two peaks: most often, psoriasis occurs at the age of 16-22 or 57-60 years, but it is possible at any age. What causes psoriasis is known, but is usually traced in family history. HLA antigens (CW6, B13, B17) are associated with psoriasis. It is assumed that exposure to external factors causes an inflammatory reaction and subsequent hyperproliferation of keratinocytes. It is well known that psoriasis is triggered by factors such as: skin lesions (Koebner phenomenon), solar erythema, HIV, beta-hemolytic streptococcal infection, medications (especially beta-blockers, chloroquine, lithium, angiotensin-converting enzyme inhibitors, indomethacin, terbinafine, and alpha interferon), emotional stress, and alcohol.
Psoriasis: pathomorphology of the skin
Significant acanthosis, presence of elongated thin and somewhat thickened in the lower part epidermal outgrowths; above the tops of the dermal papillae the epidermis is thinned, sometimes consists of 2-3 rows of cells. Parakeratosis is characteristic, and in old foci - hyperkeratosis; often the stratum corneum is partially or completely peeled off. The granular layer is expressed unevenly, under areas of parakeratosis, as a rule, it is absent. During the period of progression in the spinous layer, inter- and intracellular edema, exocytosis with the formation of focal accumulations of neutrophilic granulocytes are noted, which, migrating into the stratum corneum or parakeratotic areas, form Munro microabscesses. Mitoses are often found in the basal and lower rows of the spinous layers. According to the lengthening of the epidermal processes, the papillae of the dermis are enlarged, flask-shaped, dilated, edematous, the capillaries in them are twisted, filled with blood. In the subpapillary layer, in addition to dilated vessels, a small perivascular infiltrate of lymphocytes, histiocytes with the presence of neutrophilic granulocytes is noted. In exudative psoriasis, exocytosis and intercellular edema in the epidermis are sharply expressed, which leads to the formation of Munro microabscesses. In the regressing stage of the process, the listed morphological signs are expressed much less strongly, and some are completely absent.
In psoriatic erythroderma, there are histological changes typical of psoriasis, but in some cases there is a pronounced inflammatory reaction with the presence of eosinophilic granulocytes among the cells of the inflammatory infiltrate. Spongiosis and vesiculation are sometimes encountered. In addition, the scales are often weakly attached to the epidermis and are separated during treatment with the preparation along with microabscesses.
Pustular psoriasis is characterized by lesions of the skin of the palms and soles; the generalized form of the disease is much less common. The exudative inflammatory reaction, accompanied by vesiculation, is so pronounced that it sometimes obscures the histological signs typical of psoriasis. As a rule, there are a lot of Munro microabscesses, which are located not only under the horny layer, but also in the Malpighian layer of the epidermis. The histological picture of acute generalized pustular psoriasis of Numbush is characterized by the presence of subhorny pustules and destruction of the upper parts of the spinous layer, infiltrated by neutrophilic granulocytes with the formation of a spongiform pustule of Kogoy. There are disagreements in the assessment of histological changes in the skin in generalized pustular psoriasis. Some authors consider the characteristic feature of this process to be the presence of histological signs of psoriasiform acanthosis and hyperkeratosis, while others consider changes that differ from psoriasis. The most characteristic general histological feature of pustular forms of psoriasis are spongiform pustules of Kogoy, which are small cavities in the spinous layer filled with neutrophilic granulocytes. In such cases, it is necessary to carry out differential diagnostics of pustular psoriasis from herpetiform impetigo, gonorrheal keratosis, Reiter's disease, and subcorneal pustulosis of Sneddon-Wilkinson.
Verrucous psoriasis, in addition to acanthosis, parakeratosis, inter- and intracellular edema of the Malpighian layer, has papillomatosis and hyperkeratosis, as well as a sharply expressed exudative component with exocytosis and the formation of numerous Mynro microabscesses, in the area of which there may be massive layers of horny scales and crusts. In the dermis, a vascular reaction is usually sharply expressed with swelling of the vessel walls, their loosening and the exit of formed elements from the lumens of the vessels. The dermis, especially in the upper sections, is sharply edematous.
Psoriasis: histogenesis
The question of the leading role of epidermal or dermal factors in the development of the disease has not yet been resolved, but the main role, as a rule, is assigned to epidermal disorders. It is assumed that there is a genetic defect in keratinocytes, leading to hyperproliferation of epidermal cells. At the same time, dermal changes, primarily vascular, are a more constant feature of psoriasis, they appear earlier than epidermal ones and persist for a long time after treatment. Moreover, dermal changes are detected in clinically healthy skin of patients and their first-degree relatives. With clinical recovery from psoriasis, only epidermal disorders are normalized, and the inflammatory process persists in the dermis, especially in the vessels.
The role of biochemical factors (chalones, nucleotides, arachidonic acid metabolites, polyamines, proteases, neuropeptides, etc.) has been studied for many years; however, none of the detected biochemical disorders has been given etiological significance.
The contribution of the study of immune mechanisms to the development of the inflammatory reaction is significant. It is assumed that the occurrence of a cellular infiltrate consisting mainly of the CD4 subpopulation of T lymphocytes is a primary reaction. The genetic defect can be realized at the level of antigen-presenting cells, T lymphocytes, which leads to a different than normal production of cytokines, or at the level of keratinocytes that react pathologically to cytokines. As a confirmation of the hypothesis about the important role of the activated CD4 subpopulation of T lymphocytes in the pathogenesis of psoriasis, a positive effect of the use of myoclonal antibodies to CD4 T lymphocytes, normalization of the ratio of CD4+/CD8+ T lymphocyte subpopulations after psoriasis treatment is given.
The histogenesis of generalized pustular psoriasis is also unclear. In cases where it develops as a result of drug use, an immediate hypersensitivity reaction is assumed to play a role. The important role of immune system disorders is indicated by changes in the vessels at the sites of pustule formation, the presence of IgG, IgM, IgA and complement component C3 deposits in the pustules and complement component C3b in the basement membrane of the epidermis, changes in the surface receptors of neutrophil granulocytes obtained from pustules, T-system insufficiency of the immune system, a decrease in the T-helper/T-suppressor ratio and the activity of natural killers in the blood.
Symptoms of Psoriasis
The lesions are either not accompanied by subjective sensations or have mild itching, and are most often localized on the scalp, extensor surfaces of the elbows and knees, sacrum, buttocks, and penis. The nails, eyebrows, armpits, umbilical area, and/or perianal area may also be affected. Psoriasis can become widespread, involving large areas of the skin. The appearance of the lesions depends on the type. Plaque psoriasis is the most common type of psoriasis, in which oval erythematous papules or plaques covered with dense silvery scales are formed.
The lesions appear gradually, disappear, and recur spontaneously or as a consequence of causative factors. There are subtypes and they are described in Table 116-1. Arthritis develops in 5-30% of patients, which can lead to disability. Psoriasis is rarely life-threatening, but it can affect the patient's self-esteem. In addition to low self-esteem, constant care of the affected skin, clothing, and bedding can adversely affect the quality of life.
What's bothering you?
How is psoriasis recognized?
The diagnosis of psoriasis is most often made based on the appearance and location of the lesions. Psoriasis must be differentiated from seborrheic eczema, dermatophytosis, chronic lupus erythematosus, lichen planus, lichen rosea, basal cell carcinoma, Bowen's disease, lichen simplex chronicus, and secondary syphilis. Biopsy is rarely necessary and is not used for diagnosis. The severity of the disease (mild, moderate, or severe) largely depends on the nature of the lesions and the patient's ability to cope with the disease.
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Psoriasis: treatment
Given the pathogenesis of psoriasis, therapy should be aimed at correcting inflammation, hyperproliferation of epithelial cells and normalizing their differentiation. Currently, there are many methods and various drugs for the treatment of psoriasis. When prescribing a particular method of treatment, it is necessary to approach each patient individually, taking into account gender, age, profession, stage, clinical form, type of disease (summer, winter), prevalence of the process, concomitant and past diseases, previously received therapy.
Common psoriasis is often treated with traditional, generally accepted methods, which include the administration of hyposensitizing (calcium chloride, calcium gluconate, sodium thiosulfate), antihistamines (fenistil, tavegil, diazolin, analergin, etc.), vitamin (PP, C, A and group B) drugs, hepatoprotectors, agents that improve microcirculation, etc.
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