Psoriasis

Psoriasis is a chronic inflammatory skin condition characterised by the presence of well-defined, red, and scaly plaques. This skin disorder impacts approximately 2-4% of the global population regardless of gender. While it can emerge at any age, there are distinct peaks of onset between ages 15-25 and 50-60, making psoriasis a condition that endures a lifetime while varying in terms of severity and extent during different periods. Approximately one-third of individuals diagnosed with psoriasis have a family history of this skin condition.

This condition is classified as an immune-mediated inflammatory disease (IMID), driven by multifactorial factors in which genetics play a pivotal role. Genome-wide association studies have established an association between the histocompatibility complex HLA-C*06:02 (formerly known as HLA-Cw6) and early-onset and guttate psoriasis. However, this genetic marker is not linked to arthritis, late-onset psoriasis, or nail dystrophy.

The clinical features of psoriasis are attributed to immune factors and inflammatory cytokines, such as IL1β and TNFα. Research is currently examining the TH17 pathway and the release of the cytokine IL17A as potential contributors to the condition.

Typically, psoriasis manifests as red and scaly plaques with well-defined edges and symmetric distribution across affected areas of the skin. The scales are usually silvery white, but they take on a shiny appearance with a moist-peeling surface in skin folds. The most commonly affected areas include the scalp, elbows, and knees, but psoriasis can affect any part of the skin. Without proper treatment, these plaques tend to become persistent, leading to discomfort.

Although most patients report mild itching, some may experience more severe itching, resulting in excessive scratching and lichenification. This phenomenon causes the skin to thicken and become leathery, marked by an increase in skin markings. Painful skin cracks or fissures may also develop.

Upon resolution of psoriatic plaques, pale or brown marks may be left behind, which are generally expected to fade over several months.

Key features are considered when determining the most appropriate investigations and treatment methods for psoriasis, taking into account that overlaps may occur. These features include early age of onset (under 35) versus late age of onset (over 50), with early onset prevalent in 75% of reported cases. Other features encompass acute (e.g., guttate psoriasis) versus chronic plaque psoriasis, localised (e.g., limited to the scalp area) versus generalised psoriasis, small plaques (under 3 cm) versus larger plaques (over 3 cm), thin plaques versus thick plaques, and the presence or absence of nail involvement.

Risk Factors

Several potential risk factors can trigger the onset of psoriasis, including:

• Injuries such as cuts, sunburn, and abrasions
• Dry skin
• Obesity
• Smoking
• Heavy alcohol consumption
• Medications such as beta-blockers and lithium
• Discontinuation of oral steroids or potent topical corticosteroids
• Stressful events
• Metabolic syndrome, including obesity, type 2 diabetes, hypertension, and hyperlipidaemia

Diagnosis and Assessment

Diagnosing and assessing psoriasis involves a meticulous examination and a comprehensive patient history. The impact of psoriasis on daily life activities is evaluated, and comorbid factors are taken into consideration.

Treatment

Mild psoriasis is typically managed with prescribed topical agents tailored to the affected body site, extent, and severity. For moderate to severe psoriasis, systemic agents such as Methotrexate in combination with phototherapy are commonly employed.