Learning Center

What Is Psoriasis?

Psoriasis is a common condition affecting the skin, nails and joints. It causes red, scaly patches, yellow, pitted, crumbling nails, and joint pain with morning stiffness. The most commonly affected areas are the scalp, elbows, and knees. The skin is usually red, thickened and crusty, often with silvery flakes which are easily removed. Psoriasis is not infectious or contagious. It cannot be caught or spread by contact. 2% of people (1 in 50) have psoriasis to some degree.

Patch and Plaque Psoriasis

Patches and plaque of psoriasis consist of areas of skin that are uniformly and totally red thickened and scaly. The difference between a patch and a plaque of psoriasis is only one of size. A patch of psoriasis may be the size of the silver dollar, and a plaque of psoriasis the size of a dinner plate.

Guttate Psoriasis

The word guttate is derived from the Latin, “gutta” meaning “drop-like”. Guttate psoriasis is characterized by tiny patches of psoriasis distributed widely over the body.

Flexural Psoriasis

The psoriasis is in skin folds e.g. under breasts, between buttocks etc.

Pustular Psoriasis

Small pustules appear on the palms of the hands and soles of the feet.

Scalp Psoriasis

Scaling and flaking of the scalp.

Erythrodermic Psoriasis

A serious, but rare, complication of psoriasis is erythroderma, where large areas of the skin become hot, red, and dry. This is one of the few emergencies involving skin conditions. If you suffer from this your doctor may admit you to hospital.

Psoriatic Arthritis

Said can be affected by psoriatic arthritis. Those most affected are the small joints of the hand and the sacroiliac joint of the low back. Patients can also experience generalized morning stiffness.

Psoriatic Nails

Any or all of your fingernails or toenails may develop pits, or become thickened, opaque, with yellow spots. The nail plates may separate from the nail bed and crumble apart. This condition can be confused with a fungus infection of the nails.


The cause of psoriasis is unknown. Current scientific knowledge suggests that there is an abnormality of the immune system. “Activated” white blood cells called “T-helper cells” migrate from the blood vessels into the skin, where they trigger inflammation and rapid skin growth. Normal skin replaces itself, by pushing up new skin cells from below over a period of 28 days, but in psoriasis this takes as little as 4 days. This accounts for the red color, thickening, and scaliness that are the hallmarks of psoriasis.

Psoriasis runs in some families, but that is not to say that everyone in a family will get it. It can start at any stage in life. Sometimes a patch will start where the skin has been injured (Köbner phenomenon). A throat infection and certain medications can trigger the onset of psoriasis, or a flare-up of existing psoriasis.


Your doctor will usually make the diagnosis of psoriasis from the appearance of the rash. In case of doubt, a biopsy will be sent to the laboratory. If you have inflamed joints, your doctor may want to arrange some blood tests.


There is no “cure” for psoriasis, but many people have long periods when it does not trouble them. Sometimes it gets better on its own, but most people need some treatment. For years, the mainstay of treatment has been the topical application of lotions creams, or ointments containing cortisone. Topical preparations based on Vitamin D (e.g., Calcipotriol) are occasionally effective. Moisturizing creams and ointments are used to moisturize dry skin.

Systemic medications include cortisone, methotrexate, cyclosporine, acetretin. These medications all have manageable side effect profiles that require regular monitoring by your doctor.

An exciting new class of medications called “biologicals” has recently become available. These new medications interfere with the activation and transport of T-helper cells. They are all given by injection by the physician, or by the patient at home. They all have much more patient friendly side effect profiles than the other systemic medications above listed.


No prevention is known.