Psoriasis. Epidemiology, presentation, complication and management.
Definition: • Psoriasis is a chronic, non-infectious inflammatory dermatosis characterized by well-demarcated erythematous plaques topped by silvery scales.
Epidemiology: • Psoriasis affects 2% of the population in Europe and North America, but is less common in Africa and Japan. • The sex incidence is equal. • The condition may start at any age, even in the elderly, but the peak onset is in the 2nd and 3rd decades. It is unusual in children less than 8 years old.
Aetiopathogenesis: • Genetics: about 35% of patients show a family history, andidentical twin studies show a concordance of 80%. There are strong correlations with the HLA antigens CW6, B13 and B17. • Epidermal kinetics and metabolism. The epidermal cell proliferation rate is increased 20 fold or more in psoriasis, and the germinative cell population is expanded.
Precipitating factors: • Koebner phenomenon. Trauma to the epidermis and dermis, such as scratch or surgical scar can precipitate psoriasis in the damaged skin. • Infection. Typically, a streptococcal sore throat may precipitate guttate psoriasis. • Drugs. Beta-blockers, lithium and antimalarials. • Sunlight. • Psychological stress.
Clinical presentation. • Psoriasis varies in severity from the trivial to the life-threatening. • Presentation patterns of psoriasis include: • Plague. • Guttate. • Flexural. • Localized forms. • Generalized pustular. • Nail involvement. • Erythoderma.
Plaque. • Well-defined, disc-shaped plaques involving the elbows, knees, scalp hair margin or sacrum are the classic presentation. The plaques are usually red and covered by waxy white scales which if which, if detached may leave bleedng points.
Guttate. • Guttate psoriasis is an acute symmetrical eruption of “drop-like” lesions usually on the trunk and limbs. The form mostly occurs in adolescents or young adults and may follow a streptococcal throat infection.
Localized forms. • Psoriasis can also present in a number of localized forms: • Palmoplantar pustulosis. • Acrodermatitis of Hallopeau. • Scalp psoriasis. • Napkin psoriasis.
Generalized pustular. • Generalized pustular is a rare but serious and even life-threatening form of psoriasis. Sheets of small, sterile yellowish pustules develop on an erythematous background and may rapidly spread. The onset is often acute. The patient is unwell, with fever and malaise, and requires hospital admission.
Nail involvment. • Psoriasis affects the matrix or nail bed in up to 50% of cases. An oily or salmon pink discoloration of the nail bed is seen, often adjacent to onycholisis.
TREATMENT • Topical therapy: 1. topical corticosteroids 2. vit D analogues – dovonex. 3. keratolytic and scalp preparations – salicylic acid ointment. • systemic therapy: 1. PUVA. 2. retinoids 3. methotrexate. 4. cyclosporin.