Psoriasis is a noncontagious noncurable common long term skin condition that causes rapid skin cell reproduction resulting in red, itchy, dry patches and thick silvery scales of thickened skin. The dry flakes and skin scales are thought to result from the rapid buildup of skin cells. Psoriasis commonly affects the skin of the elbows, knees, and scalp. Sometimes psoriasis may clear for years and stay in remission. Some have worsening of their symptoms in the colder winter months. Many show improvement in warmer climates, or with increased sunlight exposure. Patients with more severe psoriasis may have social embarrassment, job stress, emotional distress, and other personal issues because of the appearance of their skin.

Symptoms

Psoriasis signs and symptoms can vary from person to person but may include one or more of the following:

• Red patches of skin covered with silvery scales
• Small scaling spots (commonly seen in children)
• Dry, cracked skin that may bleed
• Itching, burning or soreness
• Thickened, pitted or ridged nails
• Swollen and stiff joints

Most types of psoriasis go through cycles, flaring for a few weeks or months, then subsiding for a time or even going into complete remission. In most cases, however, the disease eventually returns.

Types of psoriasis are:

• 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 body, including genitals and the soft tissue inside your mouth.

• 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 covered by fine scales.
• Inverse psoriasis. Mainly affecting the skin in the armpits, 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. Generalized pustular psoriasis can also cause fever, chills, severe itching and fatigue.

 

Causes

The cause of psoriasis is related to the immune system, and more specifically, a type of white blood cell called a T lymphocyte or T cell that detect and fight off foreign substances, such as viruses or bacteria. Overactive T cells trigger other immune responses including dilation of blood vessels in the skin around the plaques and an increase in other white blood cells that can enter the epidermis. These changes result in an increased production of both healthy skin cells and more T cells and other white blood cells. What results is 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.

Psoriasis triggering factors

Psoriasis typically starts or worsens because of a trigger that you may be able to identify and avoid. Factors that may trigger psoriasis include:

Infections, such as strep throat or thrush

• Injury to the skin, such as a cut or scrape, bug bite, or severe sunburn
• Stress
• Cold weather
• Smoking
• Heavy alcohol consumption
• Certain medications — including lithium, which is prescribed for bipolar disorder; high blood pressure medications such as beta blockers; antimalarial drugs; and iodides

Tests and diagnosis

History taking

Signs and symptoms

Taking a small sample of skin (biopsy) that's examined under a microscope to determine the exact type of psoriasis and to rule out other disorder.