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  • An autoimmune disease that results in recurring red, scaly, and itchy patches of skin
  • Types: plaque, guttate, pustular, erythrodermic, and inverse
  • Treatment may involve light therapy, topical and oral medications, as well as biologics
  • Involves Medical Dermatology, Pediatric Dermatology, and Pathology


Psoriasis is an autoimmune disease that results in red, scaly, itchy patches of skin that often recur even after successful treatment.

The condition tends to show up from the ages of 20 to 30 and then again, sometimes for the first time, from ages 50 to 60. Psoriasis is one of the best understood skin diseases, and a number of proven therapies are available. 

Yale Medicine has leading experts in this condition who take on the most challenging cases, using precision and creativity to help people recover.

What are the symptoms of psoriasis?

Psoriasis typically shows up as scaly, itchy patches, most commonly on the elbows, knees and the lower back. The condition causes skin to grow very rapidly, developing what looks like raised, red rashes. “Areas of skin are in a sense overgrowing very rapidly, which leads to a buildup of skin and scale," says Brett King, MD, PhD, a Yale Medicine dermatologist and an assistant professor at Yale School of Medicine, who is an expert in treating autoimmune skin conditions such as psoriasis and alopecia areata. "At some point it becomes so scaly it does indeed fall off.” Depending on its type and severity, psoriasis can be localized in specific areas or cover wide swaths of skin all over the body.

Are there different kinds of psoriasis?

There are five main types of psoriasis:

  • Plaque psoriasis: The most common type of psoriasis, it usually causes dry, reddened skin lesions covered in white scaly skin.
  • Guttate psoriasis: Typically seen in children or adults younger than 30, it shows up as small circular sores on the torso, arms, legs and scalp.
  • Pustular psoriasis: In this rapidly developing type of psoriasis, pustules develop on top of reddened skin, either widespread or localized on hands, feet and fingertips.
  • Erythrodermic psoriasis: The rarest type of psoriasis, it causes a red, scaly rash that covers the entire body.
  • Inverse psoriasis: Smooth patches of reddened skin appear in the creases of the groin, armpits and under the breasts in women. It’s more common in overweight people and made worse by friction and sweating.

What are the risk factors for psoriasis?

It’s important to draw a distinction between risk factors for developing psoriasis and triggers that will bring on or worsen the condition. The only proven determinant in whether a person will develop psoriasis is hereditary—whether there is a family history. But factors that could bring on or exacerbate psoriasis include: being overweight, illness or infection, skin injury and alcohol or tobacco use.

“It’s not that being obese gives you psoriasis. It’s not that smoking tobacco gives you psoriasis," says Dr. King. "It’s that those things are factors that probably make it harder to control psoriasis.”

How is psoriasis diagnosed?

Psoriasis is usually diagnosed by a dermatologist. Occasionally, if there’s something confusing about the skin’s appearance, a dermatologist will perform a biopsy to confirm the diagnosis. Biopsies are helpful diagnostic tools in dermatology because each specific skin disease has a characteristic appearance under the microscope.

How is psoriasis treated?

Compared with many diseases of the skin, psoriasis is easy to treat.

Treatment for psoriasis ranges from topical medicines such as steroids and vitamin creams to light therapy and systemic oral medications.

Light therapy exposes patients to narrow-band ultraviolet B (UVB) light of a specific wavelength that reduces the overgrowth of immune cells, thereby preventing them from building up into the scaly patches psoriasis causes.

In the past, there were two medicines, Trexall (methotrexate) and Soriatane (acitretin), commonly used to treat psoriasis systemically. But in the last decade, as researchers have made dramatic strides in understanding psoriasis, another class of medications, called biologics, has been developed. Biologics mimic our own antibodies’ behavior in removing specific molecules from circulation within the body.

Still, even with advanced treatments on the market and in development, remissions longer than a few years remain elusive, while permanent remissions haven’t yet been achieved. 

“With psoriasis, we’re getting closer and closer to really dramatic remissions,” Dr. King says. “But for the most part, these things are treatments. While you use them you get a good result. If you stop them, you might get a break but it’s going to come back.”

What makes Yale Medicine’s approach to treating psoriasis unique?

Treatments for psoriasis are generally consistent, based on the newest and most effective therapies available. But Yale Medicine is often a destination for the worst cases of the condition, so treatment here needs to be precise and creative. 

“People with the worst psoriasis, those are the people who end up in my care,” says Dr. King.