Psoriasis: Symptoms, Causes & Treatment

Psoriasis is a chronic immune-mediated inflammatory disease affecting approximately 2–3% of the global population. It is characterized by dysregulated keratinocyte proliferation — skin cells turn over in days rather than weeks — producing the characteristic raised, erythematous plaques covered with silvery-white scales. Psoriasis is now recognized as a systemic disorder with associations with psoriatic arthritis (in up to 30% of patients), cardiovascular disease, metabolic syndrome, and psychiatric comorbidities including depression.

Plaque psoriasis is the most common form, accounting for over 80% of cases, with well-demarcated erythematous plaques most frequently on the knees, elbows, scalp, and lumbosacral region. Other clinical variants include guttate (raindrop-like lesions, often triggered by streptococcal infection), inverse (flexural areas), pustular, and erythrodermic psoriasis — the last being a medical emergency. Disease course is characterized by remissions and flares triggered by stress, infections, medications, skin trauma (Koebner phenomenon), or smoking.

Modern pathophysiology centers on a dysregulated T-helper (Th17/Th1) immune axis releasing pro-inflammatory cytokines — IL-17A, IL-23, and TNF-α — that drive keratinocyte hyperproliferation. This understanding underpins targeted biologic therapies that achieve clear or almost-clear skin in the majority of patients, representing a paradigm shift from older systemic treatments.

• Well-demarcated red, raised plaques with silvery-white scales (plaque type)
• Pruritus, burning, and soreness in affected areas
• Skin cracking and pinpoint bleeding when scales are removed (Auspitz sign)
• Nail changes: pitting, onycholysis, yellow-brown discoloration
• Joint pain and stiffness suggesting psoriatic arthritis

• Genetic predisposition: over 25 susceptibility loci including HLA-Cw6
• Immune dysregulation: overactive Th17/Th1 axis with excess IL-17A, IL-23, TNF-α
• Environmental triggers: streptococcal infection (especially guttate), stress, smoking, alcohol
• Drug triggers: lithium, beta-blockers, antimalarials, NSAIDs, IFN-α
• Skin trauma triggering the Koebner (isomorphic) phenomenon

• A family history of psoriasis.
• Chronic stress, smoking, and obesity.
• Some infections such as strep throat.

Diagnosis is primarily clinical based on the characteristic appearance and distribution of lesions. Skin biopsy showing parakeratosis, suprapapillary thinning, and dilated capillaries confirms the diagnosis when uncertain. Workup for psoriatic arthritis (joints, imaging) and metabolic comorbidities should accompany initial assessment.

Treatment is stepped according to severity. Mild disease: topical corticosteroids, vitamin D analogues (calcipotriol), calcineurin inhibitors. Moderate-to-severe: narrowband UVB phototherapy or systemic agents (methotrexate, cyclosporine, acitretin). Biologic therapies targeting IL-17A (secukinumab, ixekizumab), IL-23 (guselkumab, risankizumab), and TNF-α (adalimumab) achieve clear or almost-clear skin in the majority of patients and are the standard of care for moderate-to-severe plaque psoriasis.

• Psoriatic arthritis (up to 30%) with risk of joint damage and disability
• Increased risk of cardiovascular disease, metabolic syndrome, and stroke
• Depression, anxiety, and significant psychosocial impairment
• Erythrodermic psoriasis: a medical emergency with thermoregulatory failure and fluid loss

• Identify and avoid personal triggers: stress, infections, smoking, alcohol
• Adhere consistently to the prescribed treatment regimen
• Skin care: daily emollients and avoidance of skin trauma (Koebner phenomenon)
• Maintain healthy weight — obesity worsens severity and reduces biologic efficacy