Symptoms

Doctors now recognize five distinct types of psoriasis as identified by the presence of different types of psoriatic lesions. Some types can occur independently or at the same time as other variants, or one may follow another. By far, the most common type is plaque psoriasis, which often is mild and restricted to a few small patches. The most severe and rare forms are erythrodermic (exfoliative) psoriasis and generalized pustular psoriasis, both of which may require hospitalization.

Plaque psoriasis: (psoriasis vulgaris or common psoriasis) accounts for more than 80% of all cases. The term, “plaque,” defines the type of skin lesion and its appearance and size. To qualify as plaque, a raised skin lesion must be 1 cm or more in diameter. Often, psoriatic patches start off as smaller “papules” (less than a centimetre in diameter) and then either grow in size or join together to form the larger plaque. Typically, plaque psoriasis lesions are round or oval shape with red, raised borders visibly distinct from surrounding unaffected skin. Sometimes, the lesion can be ring-shaped, with a clear centre and a wavy, red border. Silver-white scales of dead skin cells accumulate on the surface of the plaque, becoming quite thick and in some cases resembling the rough surface of oyster shells. The powdery scales of dead skin flake and peel in sheets. If the scales are scratched or scraped away, pinpoints of blood appear underneath.

Although plaques can appear anywhere on the body, the elbows, knees, low back and the area around the bellybutton are the most common sites. When the patches first appear, they tend to be symmetrical, affecting both elbows or knees or the left and right sides of the low back. Although not common in either gender, men are more likely than women to develop plaques on their genitals. Psoriasis can also appear as flaky skin between the toes, which can be mistaken for athlete’s foot. Occasionally, plaques can develop on the pressure-bearing areas of the palms of the hands and soles of the feet.

About half of people with plaque psoriasis also develop lesions on their scalp, which usually begin behind the ears and along the hairline. Scalp psoriasis can be restricted to a few discrete patches or spread to cover the whole scalp. The plaques tend to form dense crusts that can be very itchy and difficult to dislodge, although the scales of dead skin flake away easily. Picking and scratching can create small sores and bleeding, and cause the psoriasis to worsen. There is one small consolation, however. Since psoriasis doesn’t involve the hair root, it rarely causes hair loss.

Plaque psoriasis frequently involves fingernails and toenails, causing them to develop tiny pits or grooves. Nails can also change in shape and colour, and sometimes they thicken and detach from the underlying nail bed. Bacterial and fungal infections can develop in a nail already affected by psoriasis. Fingernails seem to be more prone to these symptoms than toenails. While not everyone whose nails are affected by psoriasis goes on to develop arthritis, there is a very strong correlation between psoriatic arthritis and psoriatic nail symptoms.

Guttate psoriasis: typically flares up suddenly in children and teenagers one to three weeks after a bacterial throat infection (usually streptococcal pharyngitis) or tonsillitis, although this type of psoriasis can also affect adults. “Guttate” describes the red, teardrop-shaped bumps (gutta means “droplet” in Latin), two to three millimetres in diameter, that can suddenly erupt and spread rapidly over the chest, back, arms and legs, and occasionally the face. Guttate psoriasis in children often clears up after the first episode and never recurs, although some children will go on to develop plaque psoriasis. Some adults, too, will go on to develop plaque psoriasis after an episode of guttate psoriasis.

Inverse psoriasis: can occur on its own but usually appears along with plaque psoriasis. The smooth, moist, salmon-coloured appearance of the plaques and their location are what distinguishes this type of psoriasis. Also known as flexural psoriasis because it affects sites where the body folds, inverse psoriasis occurs most often on the skin in the armpits, groin, under the breasts and in the cleft between the buttocks. The patches are often tender and raw or itchy, causing great discomfort, and can be further irritated by perspiration.

Erythrodermic psoriasis: a severe and rare form, (also known as exfoliative psoriasis or psoriatic exfoliative erythroderma) causes scaly, peeling lesions to cover all or nearly all of the body. Even the eyes, lining of the mouth and inside of the nose can be affected. The skin becomes extremely red, itchy and swollen, with areas of raw skin and pustules. This type of psoriasis either evolves from longstanding plaque psoriasis that has covered more and more skin area or is triggered in people with unstable plaque psoriasis by such factors as a secondary illness, emotional stress, alcohol abuse and withdrawal from high-dose corticosteroids.

People with this condition can become quite ill and vulnerable to infection in the affected skin. They may also experience difficulty maintaining normal levels of body fluids and body temperature, which might require hospitalization until they’re stabilized. People with a prior history of heart disease and the elderly are at risk of cardiac failure, because the increased blood flow to severely inflamed skin taxes the heart’s ability to keep up with the body’s demand for oxygenated blood.

Pustular psoriasis: as the name implies, includes small lesions that are filled with pus and resemble blisters. This type of psoriasis can develop on its own or it can evolve from plaque psoriasis. There are a number of known triggers, including infections, emotional stress, certain medications and metal allergies. Pustular psoriasis comes in two forms: localized palmoplantar pustulosis, which affects the palms of the hands and the soles of the feet, and the rare generalized pustular psoriasis, which affects large areas of the body. People with the generalized form are usually gravely ill and require hospitalization until they are in stable condition. In rare cases, most of the epidermis can peel off all at once.

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