Psoriasis vulgaris

Psoriasis, Psori

A chronic, immune-mediated, systemic inflammatory disease characterized by clearly defined erythematous plaques with silvery-white scales, variable nail and joint involvement, and a wide range of cardiometabolic and psychosocial comorbidities.

• Global prevalence ≈ 2–3%; in Switzerland ≈ 2–3%.
• Bimodal age of onset: first peak at 15–35 years (type I) and second peak at 55–60 years (type II).
• Equal gender ratio; positive family history in 30–40% of cases with early onset.

• According to age at onset:
  • Type I (< 40 years, often HLA-C*06:02-positive, more severe).
  • Type II (> 40 years, milder, less familial).
• By morphology:
  • Psoriasis vulgaris (plaque type, > 90%).
  • Guttate, pustular (localized/generalized), erythrodermic, inverse, palmoplantar, cranioscapular, nail, psoriatic arthritis.

• Genetics: Polygenic; strongest association with HLA-C*06:02 (PSORS1, 6p21.3).
• Triggers: streptococcal pharyngitis, lithium, β-blockers, antimalarial drugs, NSAIDs, stress, alcohol, smoking, skin trauma (Köbner phenomenon).
• Immunology: Activation of the IL-23/IL-17 axis; key role for dendritic cells, Th17 cells, γδ T cells, tissue-resident memory T cells, and neutrophilic Munro microabscesses.

• Skin: Sharply defined erythematous plaques with silvery scales; scalp, extensor surfaces of elbows/knees, sacrum, genitals, palms, soles of feet.
• Nails: Pitting, onycholysis, oil drop sign.
• Joints: Psoriatic arthritis in 20–30%; dactylitis, enthesitis, axial disease.
• Signs: Köbner phenomenon, Auspitz sign, candle wax sign. Pruritus in ≈ 50%.
• Severe variants: erythroderma, generalized pustular psoriasis.

• Typical clinical picture ± family history.
• Screening: PEST questionnaire for arthritis.
• Biopsy: acanthosis, parakeratosis, loss of granular layer, Munro microabscesses, Kogoj spongiform pustules, dilated papillary capillaries.
• Laboratory: Baseline and control values for systemic therapy (complete blood count, liver values, kidney function, lipids).
• Differential diagnosis: Atopic dermatitis, seborrheic dermatitis, nummular eczema, pityriasis rubra pilaris, mycosis fungoides, secondary syphilis, tinea corporis.

• Adults: The scalp, extensor surfaces, and lumbosacral region are most commonly affected.
• Children: More common on the face and flexor surfaces.
• Medical history: Recurrent flare-ups, worsening in winter, improvement with sunlight, identifiable triggers, positive family history.

Regular psoriasiform hyperplasia with elongated retespitzen; confluent parakeratosis; absence of granular layer; neutrophils in the stratum corneum and spinous layer; dilated, tortuous papillary capillaries; perivascular lymphocytic infiltrates.

• Psoriatic arthritis (7–48%).
• Cardiovascular disease, metabolic syndrome, obesity, dyslipidemia.
• Depression/anxiety, NAFLD, IBD (Crohn's disease > ulcerative colitis), uveitis.

• Chronic recurrent course; lifelong disease.
• Early, sustained control improves quality of life and reduces the risk of comorbidities.
• Modern biologics achieve PASI 90/100 in >70% of patients.

• Avoidance of known triggers (infections, medications, alcohol, smoking, stress).
• Daily use of skin care products; weight control; regular exercise; smoking cessation.
• Screening for psoriatic arthritis and cardiometabolic diseases at every doctor's visit.

1. Swiss Society for Dermatology and Venereology. Swiss Psoriasis Treatment Pathway. 2024.
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6. Federal Office of Public Health. National Strategy on Noncommunicable Diseases 2023–2029. Bern; 2023.
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9. European Academy of Dermatology and Venereology. EuroGuiDerm Clinical Practice Guideline – Psoriasis 2024 Update.
10. StatPearls [Internet]. Psoriasis – Etiology, Pathophysiology, Treatment. Treasure Island (FL): StatPearls Publishing; April 3, 2023. Available at: https://www.ncbi.nlm.nih.gov/books/NBK448194/