Psoriasis is a chronic immune-mediated disease that appears on the skin. It occurs when the immune system sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of stroke. There are five types of psoriasis: plaque, guttate, inverse, pustular and erythrodermic. The most common form, plaque psoriasis, is commonly seen as red and white hues of scaly patches appearing on the top first layer of the epidermis (skin). Some patients, though, have no dermatological symptoms.
In plaque psoriasis, skin rapidly accumulates at these sites, which gives it a silvery-white appearance. Plaques frequently occur on the skin of the elbows and knees, but can affect any area, including the scalp, palms of hands and soles of feet, and genitals. In contrast to eczema, psoriasis is more likely to be found on the outer side of the joint.
The disorder is a chronic recurring condition that varies in severity from minor localized patches to complete body coverage. Fingernails and toenails are frequently affected (psoriatic nail dystrophy) and can be seen as an isolated symptom. Psoriasis can also cause inflammation of the joints, which is known as psoriatic arthritis. Between 10% and 40% of all people with psoriasis have psoriatic arthritis.
Types of psoriasis
Plaque psoriasis
The most common form, plaque psoriasis causes dry, raised, red skin lesions (plaques) covered with silvery scales. The plaques itch or may be painful and can occur anywhere on your body, including your genitals and the soft tissue inside your mouth. You may have just a few plaques or many, and in severe cases, the skin around your joints may crack and bleed.
Nail psoriasis
Psoriasis can affect fingernails and toenails, causing pitting, abnormal nail growth and discoloration. Psoriatic nails may become loose and separate from the nail bed (onycholysis). Severe cases may cause the nail to crumble.
Scalp psoriasis
Psoriasis on the scalp appears as red, itchy areas with silvery-white scales. You may notice flakes of dead skin in your hair or on your shoulders, especially after scratching your scalp.
Guttate psoriasis
This primarily affects people younger than 30 and is usually triggered by a bacterial infection such as strep throat. It’s marked by small, water-drop-shaped sores on your trunk, arms, legs and scalp. The sores are covered by a fine scale and aren’t as thick as typical plaques are. You may have a single outbreak that goes away on its own, or you may have repeated episodes, especially if you have ongoing respiratory infections.
Inverse psoriasis
Mainly affecting the skin in the armpits, in the groin, under the breasts and around the genitals, inverse psoriasis causes smooth patches of red, inflamed skin. It’s more common in overweight people and is worsened by friction and sweating.
Pustular psoriasis
This uncommon form of psoriasis can occur in widespread patches (generalized pustular psoriasis) or in smaller areas on your hands, feet or fingertips. It generally develops quickly, with pus-filled blisters appearing just hours after your skin becomes red and tender. The blisters dry within a day or two, but may reappear every few days or weeks. Generalized pustular psoriasis can also cause fever, chills, severe itching and fatigue.
Erythrodermic psoriasis
The least common type of psoriasis, erythrodermic psoriasis can cover your entire body with a red, peeling rash that can itch or burn intensely. It may be triggered by severe sunburn, by corticosteroids and other medications, or by another type of psoriasis that’s poorly controlled.
Psoriatic arthritis
In addition to inflamed, scaly skin, psoriatic arthritis causes pitted, discolored nails and the swollen, painful joints that are typical of arthritis. It can also lead to inflammatory eye conditions, such as conjunctivitis. Symptoms range from mild to severe, and psoriatic arthritis can affect any joint. Although the disease usually isn’t as crippling as other forms of arthritis, it can cause stiffness and progressive joint damage that in the most serious cases may lead to permanent deformity.
What Are The Symptoms of Psoriasis?
Symptoms of psoriasis can differ in severity, frequency and duration among individuals. Symptoms can occur at any age. If you have psoriasis, your symptoms may be minimal and include infrequent outbreaks, or you may experience more frequent breakouts on larger areas of skin.
Outbreaks of psoriasis include patches of raised areas of itchy, red or pink thickened skin and lesions that are covered with whitish scales. Scratching the area affected by psoriasis generally does not relieve the itching and can lead to increased inflammation, more intense itching, and harder scratching.
Symptoms of psoriasis most often affect the:
- Elbows
- Knees
- Lower back
- Scalp
- Soles of the feet
Psoriasis can also affect the:
- Area round the genitalia
- Areas under the breasts
- Armpits
- Feet
- Hands
Psoriasis can also affect the nails and can result in:
- Nail separation from the skin
- Pitting of the nails
- Thickening of the nails
Complications of Psoriasis
About one in four people with psoriasis also develop joint disease. Usually the joints at the end of your fingers and toes are affected, although your back, knees and hips may be affected too.
Cause of Psoriasis
If you have psoriasis, substances produced by your immune system cause your skin to start producing new cells faster than usual. This causes your skin to thicken and become scaly. What makes your immune system act like this isn’t clear.
More specifically, one key cell is a type of white blood cell called a T lymphocyte or T cell. Normally, T cells travel throughout the body to detect and fight off foreign substances, such as viruses or bacteria. If you have psoriasis, however, the T cells attack healthy skin cells by mistake, as if to heal a wound or to fight an infection.
Overactive T cells trigger other immune responses. The effects include dilation of blood vessels in the skin around the plaques and an increase in other white blood cells that can enter the outer layer of skin. These changes result in an increased production of both healthy skin cells and more T cells and other white blood cells. This causes an ongoing cycle in which new skin cells move to the outermost layer of skin too quickly — in days rather than weeks. Dead skin and white blood cells can’t slough off quickly enough and build up in thick, scaly patches on the skin’s surface. This usually doesn’t stop unless treatment interrupts the cycle.
