Psoriasis

Psoriasis
source
Name	Psoriasis
Caption	Plaque psoriasis on the back
Field	Dermatology
Symptoms	Red, itchy, scaly patches of skin
Complications	Psoriatic arthritis, Metabolic syndrome, Cardiovascular disease
Onset	Any age, often in adulthood
Duration	Chronic
Types	Plaque, guttate, inverse, pustular, erythrodermic
Causes	Genetic predisposition triggered by environmental factors
Risks	Family history, smoking, obesity, stress, certain infections
Diagnosis	Based on appearance, sometimes skin biopsy
Treatment	Topical therapy, phototherapy, systemic medications
Medication	Corticosteroids, Vitamin D analogues, Methotrexate, Biologic therapy
Prognosis	Manageable long-term condition

Psoriasis is a chronic, immune-mediated skin disorder characterized by the rapid buildup of skin cells, leading to scaling and inflammation. It is a non-contagious condition with a significant genetic component, often triggered by environmental factors. The disease manifests in several forms, with plaque psoriasis being the most common, and is associated with several comorbid conditions, significantly impacting quality of life.

Signs and symptoms

The hallmark sign is well-demarcated, erythematous plaques covered with silvery-white scales, commonly appearing on the scalp, elbows, knees, and lower back. Patients frequently report pruritus and pain, with the plaques sometimes cracking and bleeding. In psoriatic arthritis, which affects a subset of patients, symptoms extend to joint pain, stiffness, and swelling, often in the distal interphalangeal joints of the hands and feet. Other forms present distinct symptoms: guttate psoriasis with small, drop-like lesions often following streptococcal pharyngitis; pustular psoriasis with sterile pustules; and erythrodermic psoriasis with widespread redness and exfoliation, a potentially life-threatening emergency. Nail changes, including pitting, onycholysis, and oil-drop spots, are also common.

Causes and risk factors

The etiology involves a complex interplay of genetic susceptibility and environmental triggers. Genome-wide association studies have identified susceptibility loci within the PSORS1 locus on chromosome 6, particularly involving genes like HLA-Cw6. The immune dysfunction is primarily driven by a T_H1 and T_H17 mediated response, with key cytokines like TNF-α, IL-17, and IL-23 promoting inflammation and keratinocyte hyperproliferation. Common triggers include physical trauma (the Koebner phenomenon), infections like Streptococcus pyogenes, psychological stress, smoking, obesity, and certain medications such as lithium, beta blockers, and antimalarial drugs. A family history remains a strong risk factor.

Diagnosis

Diagnosis is primarily clinical, based on the characteristic appearance and distribution of the lesions. Dermatologists typically do not require laboratory tests for classic presentations. When the diagnosis is uncertain, a skin biopsy can be performed, revealing histopathological features such as parakeratosis, Munro's microabscesses, regular acanthosis, and dilated capillaries in the dermal papillae. Differential diagnosis includes conditions like seborrheic dermatitis, lichen planus, pityriasis rosea, and cutaneous T-cell lymphoma. The assessment of psoriatic arthritis may involve referral to a rheumatologist and imaging studies such as radiography or magnetic resonance imaging.

Treatment

Treatment is tailored to disease severity, type, and patient impact. First-line therapy for mild to moderate disease involves topical agents like corticosteroids, calcipotriol (a vitamin D analogue), calcineurin inhibitors such as tacrolimus, and coal tar. For moderate to severe disease, options include phototherapy using narrowband UVB or PUVA, and systemic therapies. Traditional systemic agents include methotrexate, ciclosporin, and acitretin. Biologic agents that target specific immune pathways, such as TNF inhibitors (e.g., adalimumab, etanercept), IL-12/23 inhibitors (e.g., ustekinumab), IL-17 inhibitors (e.g., secukinumab, ixekizumab), and IL-23 inhibitors (e.g., guselkumab), have revolutionized treatment. Newer oral small molecules like apremilast (a PDE4 inhibitor) are also used.

Epidemiology

Psoriasis affects approximately 2-3% of the global population, with prevalence varying geographically; rates are higher in colder climates and among populations of European descent. The incidence shows a bimodal age distribution, with peaks of onset between 20-30 and 50-60 years. It occurs equally in men and women. The disease is associated with a significant burden of comorbid conditions, including an increased risk of cardiovascular disease, type 2 diabetes, inflammatory bowel disease (particularly Crohn's disease), metabolic syndrome, depression, and anxiety. The economic impact, from direct healthcare costs and lost productivity, is substantial.

History and culture

Descriptions of psoriatic-like conditions appear in ancient texts, including those of the Greek physician Hippocrates, who used the term "lopoi" for scaly conditions. The Roman encyclopedist Aulus Cornelius Celsus described it in *De Medicina*. The modern term "psoriasis" was coined by the Austrian physician Ferdinand von Hebra, a founder of the Vienna School of Dermatology, in the 19th century. Historical treatments were often harsh, involving arsenic, mercury, and carcinogenic forms of coal tar. Public perception has been marred by stigma and misconceptions about contagion. Notable figures who have had psoriasis include the American statesman Winston Churchill, who reportedly called it his "enemy within," and the contemporary American cardiologist and television personality Dr. Oz. Awareness campaigns are led by organizations like the National Psoriasis Foundation and the International Federation of Psoriasis Associations.

Category:Dermatology Category:Immune system disorders Category:Autoimmune diseases