Psoriasis

What happens in psoriasis

In psoriasis, overactive immune cells (particularly T cells and the IL-23/IL-17 pathway) cause inflammation in the skin. Skin cells, which normally renew over about a month, mature in just a few days and pile up on the surface, forming thick scaly plaques. Blood vessels widen, causing redness. The same inflammation can affect joints, blood vessels and other organs, which is why psoriasis is considered a systemic disease.

Types of psoriasis

Symptoms

• Raised, red or discolored, scaly patches
• Silvery-white scale that may flake
• Itching, burning or soreness
• Dry, cracked skin that may bleed
• Nail pitting, ridges, thickening or separation
• Scalp scaling and flaking
• Joint pain, swelling and stiffness if psoriatic arthritis develops

Psoriasis often flares and settles in cycles. Plaques may appear at sites of skin injury, such as scratches or tattoos (the Koebner phenomenon).

Causes and triggers

Psoriasis results from a combination of genetic susceptibility and environmental triggers. About a third of people have a family history.

Common triggers:

• Infections, especially strep throat
• Stress
• Skin injury: cuts, scratches, sunburn, tattoos
• Smoking and heavy alcohol use
• Obesity
• Cold, dry weather
• Medicines: lithium, beta-blockers, antimalarials, and stopping oral steroids
• Hormonal changes

Psoriasis vs eczema

Scalp psoriasis is also distinguished from seborrheic dermatitis, which has greasier, yellowish scale.

Related conditions

• Psoriatic arthritis: affects up to 30% of people with psoriasis. Symptoms include joint pain, stiffness, swollen "sausage" fingers or toes, heel pain and back pain. Early treatment prevents joint damage
• Cardiovascular disease: higher risk of heart disease and stroke, especially with severe psoriasis
• Metabolic syndrome, diabetes and obesity
• Crohn's disease and ulcerative colitis
• Depression and anxiety
• Eye inflammation (uveitis)

Diagnosis

Psoriasis is usually diagnosed by examining the skin, scalp and nails. A skin biopsy is occasionally needed if the appearance is unusual. Doctors assess severity by body surface area affected, impact on quality of life, and involvement of sensitive areas such as the face, genitals, hands, feet and nails. They also screen for joint symptoms, blood pressure, weight, cholesterol and blood sugar.

Treatment

There is no cure, but treatment can clear or greatly reduce plaques.

Topical treatments (mild psoriasis)

• Corticosteroid creams and ointments, with strength matched to the body site
• Vitamin D analogs (calcipotriene), often combined with a steroid
• Newer non-steroid creams: roflumilast and tapinarof
• Calcineurin inhibitors for the face and skin folds
• Coal tar and salicylic acid for scale
• Medicated shampoos for scalp psoriasis
• Moisturizers daily

Phototherapy

Narrowband UVB light treatment, usually 2 to 3 times a week in a clinic or at home, helps widespread plaque and guttate psoriasis.

Oral medicines (moderate to severe)

• Methotrexate
• Cyclosporine for short-term rapid control
• Acitretin (oral retinoid), not suitable in pregnancy or for those planning pregnancy
• Apremilast (PDE4 inhibitor)
• Deucravacitinib (TYK2 inhibitor)

Biologic medicines (moderate to severe)

Injections that target specific immune pathways are highly effective, with many people achieving clear or nearly clear skin:

• TNF inhibitors: adalimumab, etanercept, infliximab, certolizumab
• IL-17 inhibitors: secukinumab, ixekizumab, brodalumab, bimekizumab
• IL-23 inhibitors: guselkumab, risankizumab, tildrakizumab
• IL-12/23 inhibitor: ustekinumab

Screening for tuberculosis and hepatitis is done before starting, and vaccines should be up to date.

Lifestyle measures

• Stop smoking and limit alcohol
• Lose weight if overweight, which can improve response to treatment
• Manage stress
• Avoid skin injury and sunburn
• Moisturize daily, especially in winter

Outlook

Psoriasis is lifelong, with flares and remissions. With modern treatment, most people can control their skin well. Regular review helps catch psoriatic arthritis early and manage cardiovascular risk.

Frequently asked questions

What are the first signs of psoriasis?

Early signs are often small red or discolored, scaly patches on the elbows, knees, scalp or lower back, sometimes itchy. Nail pitting or scalp flaking can also be early signs. Guttate psoriasis may start as many small spots after a sore throat.

Is psoriasis contagious?

No. Psoriasis is an immune condition and cannot spread from person to person through touch, swimming, sharing towels or any other contact.

What triggers a psoriasis flare?

Common triggers include infections such as strep throat, stress, skin injury, cold dry weather, smoking, heavy drinking, weight gain and certain medicines like lithium and beta-blockers. Stopping oral steroids can cause a severe flare.

What is the best treatment for psoriasis?

It depends on severity. Mild psoriasis is often controlled with steroid and vitamin D creams. Moderate to severe psoriasis may need light therapy, oral medicines or biologic injections, which clear the skin for many people.

Can psoriasis affect the joints?

Yes. Up to 30% of people with psoriasis develop psoriatic arthritis, causing joint pain, stiffness, swollen fingers or toes, heel pain and back pain. Early diagnosis and treatment prevent permanent joint damage.