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Types of psoriasis

Psoriasis comes in many forms. Each differs in severity, duration, location, shape and pattern of the scales. Usually, only one type of psoriasis appears at a time, but some people can get different types at the same time.

Plaque psoriasis

is the most common form of psoriasis. Approximately 90% of people have plaque psoriasis. It tends to be a lifelong condition that can affect many areas of the body, such as the elbows, knees, scalp, genitals, nails and lower back. The lesions are well-defined, irregularly shaped, red, can be itchy and painful with silvery scales on top which can vary in thickness and flake off easily.

Plaque psoriasis tends to be symmetrical; often if the left knee is affected so is the right knee and the plaque on the left may be roughly the same size and shape as the one on the right. It almost mirrors itself.

The scalp is often the first place that psoriasis shows up. Approximately 85-95% of people with plaque psoriasis have scalp involvement. It usually appears above the ears or back of head and may be mistaken for dandruff, or both can sometimes co-exist. Nails with psoriasis frequently have tiny pits and often lift (onycholysis). Nails may thicken or crumble, and are difficult to treat; typically systemic or biologic therapy are required to improve the nails.

Fungal infections are more common in patients with nail psoriasis and can be confused for simply “psoriatic nails.” Plaque psoriasis that occurs on the palms of the hands and soles of the feet is called palmoplantar psoriasis.

Toronto Dermatology Centre can help you determine whether you simply have psoriasis affecting your nails or an actual fungal infection; this is important as the treatment of the two conditions is vastly different.


Guttate psoriasis

is the second most common form of psoriasis and usually affects children and young adults. Typically it appears suddenly after a sore throat (e.g. Strep throat) as many small, droplet shaped, red lesions. It tends to be less scaly than plaques psoriasis and usually appears on the torso, arms and legs.

Guttate psoriasis frequently clears up by itself in a few months and may never return. However, the affected person has a higher chance of developing plaque psoriasis later in life. Phototherapy is a particularly effective option for this form of widespread psoriasis as topical cream therapy is not always practical.


Pustular psoriasis

looks like small, red, pus-filled blisters. The pus is not infectious and will not spread psoriasis from one person to another. The blisters can be painful and itchy. There are two forms of pustular psoriasis: localized and generalized. Localized pustular psoriasis typically affects the palms of the hands and the soles of the feet. Generalized pustular psoriasis can affect large areas of the body and is considered severe, as the condition can become life threatening so hospitalization may be required. Triggers can be caused by infections, stress, smoking, trauma to the skin, cold weather and certain medications. Various topical and oral therapies may be used for this form of psoriasis.


Inverse psoriasis

is also called flexural psoriasis. It occurs in the skin folds such as under the breasts, groin, armpits, abdomen, buttocks and genitals. These plaques are much less scaly than other kind of psoriasis (because of the humidity in the affected area). Flexural plaques are smooth, swollen and raw looking. Various topical therapies are typically used to treat this condition.


Erythrodermic psoriasis

is rare, but a severe kind of flare that can affect over 80% of the skins surface. The skin becomes red, itchy, swollen and sometimes pustules will form. Symptoms can include fever and chills. The skin tends to shed in large sheets. Because of the loss of large areas of skin, the body’s chemistry can become disrupted and it can become hard to maintain normal body fluid levels and body temperature so hospitalization may be required.