Psoriasis Pathophysiology Overview

Study Notes

Pathophysiology

Psoriasis is a chronic and relapsing inflammatory disorder affecting skin integrity.
Elevated levels of IL-23 in the skin are linked to autoimmune responses in psoriasis.
Antigen presenting cells release IL-23, which binds to receptors on CD4+ T cells, initiating their activation.
Activated T cells differentiate into various cytokines, with Th1 and Th17 being significant, along with memory T cells.
T cells enhance keratinocyte proliferation, inhibit their differentiation, and increase cytokine and chemokine secretion.
This leads to epidermis compromise, formation of plaques with immature keratin, and reduced desmosomes.
Memory T cells remain in the skin, providing a basis for future psoriasis episodes.

Symptoms

Plaque Psoriasis

Characterized by symmetrical lesions that are salmon pink with silvery-white scales.
Symptoms include nail pitting and separation from the nail bed.

Scalp Psoriasis

Presents with varying degrees of redness and inflammation; can be mild to severe.

Pustular Psoriasis

Exhibits sterile pustules primarily on the arms and feet.

Seborrhoeic Psoriasis

Lesions appear in the groin and armpit regions, often without scales.

Guttate Psoriasis

Features small, scattered lesions mainly on the trunk and limbs.
Commonly occurs after strep throat in adolescents and is typically self-limiting.

Erythrodermic Psoriasis

Involves extensive red skin with very few classic lesions, presenting severe systemic symptoms like fever and joint pain.

Lichen Planus

Resembles psoriasis but typically lacks a family history link.

Risk Factors

Can arise from genetic predisposition and various environmental triggers.
Key environmental factors include infections, medications, obesity, alcohol consumption, physical inactivity, smoking, and emotional stress.
Lesions may develop following trauma or stress, known as the Koebner phenomenon, where new lesions appear on previously unaffected skin.

Treatment

Severity Assessments

PASI scoring system: Mild (10), Moderate (10-20), Severe (20+).
Assessment includes body surface area and dermatology-specific quality of life index.

Topical Treatments

Corticosteroids: Used for a maximum of 8 weeks, followed by a break.
Vitamin D analogues (e.g., Calcipotriol): Prescription only; used for trunk/limbs, applied OD/BD for up to 8 weeks.
Coal tar: Available as some GSL/P; applied 2-3 times a week but may stain.
Dithranol: Start low and titrate, must be washed off after 30-60 minutes.
Salicylic acid: Used on the scalp with a thin layer for up to 3 months.

Phototherapy

Involves UVB or PUVA treatments.

Systemic Therapy

Primarily methotrexate, with other options like ciclosporin, acitretin, TNF-α, IL-12, IL-23, and IL-17 antagonists.
NICE guidelines recommend starting with a potent topical steroid and a vitamin D analogue administered at different times.

Counselling Points

Daily use of emollients is crucial; patients should find a preferred moisturizer for the entire body.
Apply emollients with smooth strokes in the direction of hair growth; carry some for dry or itchy moments.
Advise against scratching or picking at lesions, and ensure patients understand the application separation of topical treatments and emollients.
Patients should note the typical progression of treatment: scaling will resolve first, followed by a color change to normal.
Patients should cease topical treatments once the skin is clear, particularly corticosteroids.

Description

This quiz delves into the complex pathophysiology of psoriasis, focusing on its chronic inflammatory nature and the role of IL-23 in autoimmunity. It explores how activated T cells and cytokines interact with keratinocytes during the disease process. Test your understanding of these mechanisms and their implications in psoriasis treatment.

Psoriasis Pathophysiology Overview

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Questions and Answers

What cytokine is primarily associated with autoimmunity in psoriasis?

Which treatment for psoriasis should be applied for a maximum of 8 weeks before taking a break?

In which type of psoriasis are sterile pustules commonly found?

What is a common symptom of guttate psoriasis?

Which factor is NOT considered a risk factor for developing psoriasis?

How should emollients be applied for psoriasis management?

Which system is used to assess the severity of psoriasis?

What is the purpose of IL-23 in the pathophysiology of psoriasis?

Which type of psoriasis is characterized by red lesions without scales?

What phenomenon describes the development of new psoriasis lesions on previously unaffected skin after injury?