Psoriasis is a common immune-mediated polygenic inherited skin disease, typically manifested as localized or widely distributed scaly red plaques or patches. Based on the clinical characteristics, psoriasis can be classified into the following four types:
This is the most common form of psoriasis, accounting for about 90% of all cases. Typical skin lesions appear as morphologically uniform, well-defined red plaques covered with thick silvery-white scales.
When the uppermost silvery-white scales are scraped off, a layered structure resembling scraped-off wax droplets (wax drop phenomenon) can be observed. After scraping off the scales, a thin, semi-transparent “film” with a reddish glow can be seen (film phenomenon), and further peeling off the film reveals pinpoint bleeding (Auspitz sign).
Skin lesions can occur on any part of the body but usually appear on the scalp, trunk, and outer sides of the limbs, often symmetrically. They may be accompanied by varying degrees of itching.
This type is characterized by white pustules of pinhead to millet size (containing non-infectious pus), most commonly seen on the palms and fingers, and can also generalize over the entire body. Generalized pustular psoriasis is characterized by diffuse erythematous plaques and prominent sterile pustules, which can fuse to form pus lakes, often accompanied by systemic symptoms such as chills and high fever.
If secondary infection occurs, it may be life-threatening. Local forms of pustular psoriasis include palmoplantar pustular psoriasis and acrodermatitis continua of Hallopeau, with the former mainly affecting the palms and soles, and the latter usually affecting the fingertips or toenails, or both involving the nails.
This type manifests as diffuse redness, swelling, and desquamation of the skin over the entire body, accompanied by systemic symptoms such as fever and chills. The course of this type of psoriasis is prolonged and prone to recurrence. It may be caused by the improper use or withdrawal of irritant drugs or long-term and high-dose corticosteroid therapy during the progressive stage of psoriasis vulgaris.
Besides skin lesions, joint involvement may also occur, affecting any joint, such as the elbows, knees, fingers, toes, spine, and sacroiliac joints, manifesting as joint pain, swelling, and even ankylosis, but rheumatoid factor is often negative.
X-ray examination reveals the disappearance of cartilage, osteoporosis, joint space narrowing, as well as varying degrees of joint erosion and soft tissue swelling.
The exact pathogenesis of psoriasis is not fully elucidated but is known to result from the combined effects of genetic, immune, and environmental factors.
Epidemiological data, HLA analysis, and genome-wide association studies (GWAS) all support the genetic predisposition to psoriasis. Approximately 30% of psoriasis patients have a family history of the disease, and the risk of the disease is significantly increased if one or both parents have psoriasis.
GWAS has revealed associations between psoriasis and specific loci on chromosome 6p, with HLA-Cw6 being the most likely susceptibility allele at psoriasis susceptibility locus 1 (PSORS1), accounting for 50% of the heritability of the disease. Additionally, about 40 other loci are thought to be associated with psoriasis.
The skin lesions of psoriasis arise from an imbalance in the interaction between innate and adaptive components of the immune system and resident skin cell types. The core mechanisms involve the interaction between innate and adaptive immunity, particularly the central role of TNFα; Th17 cells and the IL-23/IL-17 axis; and the impact of immune responses on other cells in the skin.
Environmental factors play an important role in the induction and exacerbation of psoriasis. Factors that can trigger or exacerbate psoriasis include infections, psychological stress, mood disorders, traumatic surgeries, pregnancy, obesity, alcoholism, smoking, and certain medications.
In particular, infections, with streptococcal throat infections often associated with the onset of guttate psoriasis.
Generally, a diagnosis of psoriasis can be made through medical history inquiry, clinical manifestation observation, laboratory tests, imaging studies, and histopathological examination.
Inquiry about whether the patient has a family history of psoriasis and whether they have experienced pregnancy, obesity, smoking, or alcoholism, as these factors may induce or exacerbate psoriasis.
This is the main basis for diagnosing psoriasis. Observe whether the patient's skin has red or brownish maculopapules or plaques, whether the surface of the plaques is covered with silvery-white scales, and whether the borders are clear. Additionally, note whether the patient has joint pain, swelling, itching, or fever.
Perform blood routine examination and rheumatoid factor tests. Blood routine examination helps determine if there is secondary bacterial infection, while rheumatoid factor tests are mainly used to determine if the patient has psoriatic arthritis or rheumatoid arthritis.
The main purpose is to understand joint lesions, especially for patients suspected of having psoriatic arthritis.
This aids in the definitive diagnosis of psoriasis. The characteristics of psoriasis vulgaris include hyperkeratosis with parakeratosis, Munro microabscesses in areas of parakeratosis, significant reduction or disappearance of the granular layer, acanthosis, neatly arranged downward extension of epidermal rete pegs, thinning of the spinous layer above the papillary dermis, dilated, elongated, and tortuous capillaries surrounded by infiltrates of lymphocytes, neutrophils, etc.
Psoriasis erythrodermic is mainly characterized by more prominent dilated and congested blood vessels in the superficial dermis, with other features similar to psoriasis vulgaris. Psoriasis pustulosa manifests as Kogoj microabscesses.
The treatment of psoriasis aims to control the disease, relieve symptoms, prevent recurrence, and improve the patient's quality of life. Of particular note is the Psoriasis Area and Severity Index (PASI), an objective method for assessing the area and severity of psoriasis lesions, which helps quantify the lesion area, scale degree, infiltration degree, and redness degree, thereby facilitating graded treatment for psoriasis patients.
Suitable for patients with mild skin lesions. Common medications include glucocorticoid creams or ointments. Note that long-term use of potent formulations over a large area may cause adverse reactions, and sudden discontinuation may induce pustular or erythrodermic psoriasis.
Other topical medications such as vitamin D3 derivatives (e.g., calcipotriol), calcineurin inhibitors (e.g., tacrolimus), and keratolytic agents (e.g., salicylic acid ointment) also demonstrate significant efficacy. The combined use of these medications can effectively improve skin lesion symptoms.
For more severe skin lesions, oral medications such as methotrexate, cyclosporine, acitretin, and fumaric acid esters can be used. Additionally, emerging targeted immunomodulatory drugs (e.g., adalimumab) also show great potential. These drugs can regulate the patient's autoimmune function and promote disease recovery.
Moderate-to-severe patients may require physiotherapy in combination. For example, phototherapy, commonly used phototherapy includes narrow-band ultraviolet B (UVB) and, to a lesser extent, psoralen plus ultraviolet A (PUVA). However, due to its time-consuming nature and potential carcinogenic risk, it is usually only used for short-term disease control.
Psoriasis may cause patients to feel inferior. Therefore, psychotherapy can be employed to avoid inducing or exacerbating factors such as fatigue and mental stress, enhance patients' understanding of the disease, and guide them to undergo standard treatment.