Psoriasis is an autoimmune disease* that causes itchy, red patches of skin covered with flaky, silver-white scales. These patches are called plaques and usually appear on the knees, elbows and scalp.
It can also affect the nails (nail psoriasis), causing pitting and loosening of the nail bed. Most people with psoriasis have a mild to moderate form of the disease.
Symptoms
People with psoriasis have raised patches of itchy, flaky skin called plaques. They typically appear on the elbows, knees, scalp, trunk or limbs. They may look red with white scales on light skin or purplish, violet or brown with gray scales on darker skin. The areas are usually dry, but can bleed, rub off or scab over. Some people with psoriasis also have nail psoriasis, which causes pitting and changes in the color of fingernails or toenails. Nail psoriasis can also cause loose nails (onycholysis).
An overactive immune system causes psoriasis. It creates inflammation by mistakenly interpreting healthy cells as foreign invaders and killing them. This leads to the buildup of cells that forms the thick, scaly lesions.
There are many triggers for psoriasis, including infections, illness, stress and certain medications. For example, strep throat can lead to guttate psoriasis in children and young adults, which appears as drop-shaped spots on the torso or limbs. Other infections can trigger a flare, such as ear infections, tonsillitis, bronchitis or a cold. Certain medications can also raise your risk of psoriasis, such as blood pressure drugs like ACE inhibitors and lithium.
A severe form of psoriasis is called erythrodermic psoriasis, which covers most of the body with red, scaly skin and can be very itchy. This type of psoriasis can be life-threatening, so it’s important to see your doctor as soon as you notice symptoms.
Diagnosis
Psoriasis is usually diagnosed by a doctor examining the skin and taking a medical history. The doctor will note the size, shape, color and location of the patches. They will ask if the lesions come and go, if they are itchy or painful and if they affect your daily life. They will also look for signs of psoriatic arthritis in your joints and ask about your family’s history of the disease.
Occasionally, doctors will take a sample of the skin to test for psoriasis or other diseases that might cause similar symptoms. This is called a skin biopsy. The doctor may shave or puncture the skin with a device the size of a needle to remove a small tissue sample. The biopsy will be sent to a laboratory to be tested for psoriasis. Your doctor will numb the area with a local anesthetic before performing the procedure.
There are many different treatments for psoriasis. Over-the-counter medicines like creams, ointments and lotions can help reduce itching and scaly patches. You can also use bath oils, salts or oatmeal to relieve itching and dryness. If these treatments don’t help, your doctor may prescribe medicine in pill or injection form. These include medicines in the class of antimetabolites, like methotrexate, which works by slowing the growth and division of cells; retinoids, which are related to vitamin A and can be taken orally or applied to the skin; and immunosuppressants, which work to control the immune system.
Treatment
Your doctor can often diagnose psoriasis by looking at your skin. But they may also take a small sample of your skin to look under a microscope (biopsy). This helps confirm the diagnosis and rule out other conditions.
Your treatment plan will depend on the type and severity of your psoriasis. It can include lotions and ointments that calm the rash and reduce scales. Or it may include pills or injections that affect the immune system, not just the skin (systemic treatments). And it might include light therapy, which uses ultraviolet light to treat your psoriasis.
There are also medications that can be used on a regular basis to prevent flares and keep your symptoms under control. These include retinoids, such as tazarotene (Tazorac, Avage) and vitamin D analogues, including calcipotriene (Dovonex, Vectical), calcitriol (Vectical), and tacalcitol. These work by slowing skin-cell growth. Long-term use can cause side effects, however. These include changes in your pigmentation, easy bruising, stretch marks, and dilated surface blood vessels.
Other medications that your doctor may prescribe to help control your symptoms are antimalarial drugs, such as methotrexate (Methotrexate, Rheumatrexate), azathioprine (Imuran, Azaspiracycline), and leflunomide (Azulfidine). Your doctor might also try hydroxychloroquine (Plaquenil) or coal tar. These are used to relieve itching, but they can cause a serious liver problem in some people.
Prevention
There is no way to prevent psoriasis, but proper treatment can help control symptoms and slow the growth of thick, scaly patches. Creams, ointments, and medications applied to the skin may reduce symptoms. A doctor can recommend avoiding triggers that can cause flare-ups, such as stress, certain foods, and sun exposure. Some people also benefit from regular exercise, yoga, meditation, or other relaxation techniques.
Scientists know that psoriasis develops when genes and the immune system get out of balance. The immune system is supposed to protect the body from germs, but it overreacts and promotes the quick growth of skin cells. The extra cells form the scaly plaques of psoriasis, which are most common on the elbows and knees but can appear anywhere on the body.
Other types of psoriasis include guttate psoriasis, which causes small red spots on the skin, usually on the arms and legs. Inverse psoriasis is a less common type that affects the armpits, groin and genital area, or under a woman’s breasts. Pustular psoriasis can cause painful, blistered areas of the skin that ooze pus. And erythrodermic psoriasis can cover the entire body with a flaky, red rash.
The National Psoriasis Foundation is an organization that provides information, tips, and support for people with psoriasis. The NPF is also a leading advocate for research and awareness, particularly as it relates to people of color. It has a database to connect patients with physicians who specialize in skin of color and has an advocacy section that helps people who can’t afford medication or treatment.