Understanding Psoriasis

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Psoriasis is a chronic autoimmune skin disease affecting approximately 3% of the global population. The global prevalence of the condition is estimated to range between 100 and 125 million individuals, with a higher prevalence observed in males. This condition is characterized by erythematous plaques covered with whitish scales.

How to recognize Psoriasis?

There are several variants of psoriasis:

Psoriasis vulgaris: this is the most common form. It primarily manifests in adolescents or young adults but can also appear in children and often persists throughout life. The plaques typically occur on the knees, elbows, and scalp. They may be localized or spread over time.
Guttate Psorisis: usually presents during childhood and adolescence with small, scaly papules.
Psoriatic erythroderma: may develop following the abrupt discontinuation of immunosuppressive therapy, resulting in generalized itching, swelling, and erythema.
Pustular Psoriasis: characterized by pustules containing purulent material and pus.

Patients with psoriasis are at increased risk of developing comorbid conditions such as psoriatic arthritis, ocular diseases, metabolic and cardiovascular disorders, Crohn’s disease, type 2 diabetes, obesity, and depression.

Etiology e pathogenesis

The etiology of psoriasis remains incompletely understood; however, it is believed to involve the activation of immune and skin cells within the skin, with possible systemic effects. Both genetic and environmental factors contribute to disease onset. Common environmental triggers include skin infections, trauma, psychological stress, medication use, alcohol consumption, and tobacco smoking.

At the cellular level, psoriasis is characterized by thickening of the skin due to keratinocyte hyperproliferation. Dysregulation of keratinocyte differentiation leads to reduced expression of key proteins involved in skin homeostasis, such as loricrin and filaggrin. The dermis exhibits dilation of blood capillaries, accounting for the characteristic erythema of psoriatic lesions. There is also a significant infiltration of immune cells within the skin, including T helper cells in the dermis, cytotoxic T cells in the epidermis, macrophages and dendritic cells in both layers, and neutrophils in the stratum corneum.

The combined action of these immune and skin cells triggers chronic inflammation manifesting as epidermal hyperplasia, skin discoloration, and parakeratosis.

References: Lowes, Michelle A et al. “Pathogenesis and therapy of psoriasis.” Nature vol. 445,7130 (2007): 866-73. doi:10.1038/nature05663; Simard, Mélissa et al. “Current knowledge of the implication of lipid mediators in psoriasis.” Frontiers in immunology vol. 13 961107. 26 Aug. 2022, doi:10.3389/fimmu.2022.961107.

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