Recent research indicates that psoriasis is probably a disorder of the immune system.
The immune system includes special blood cells that identify and destroy foreign
material, including viruses and bacteria. These blood cells are called white blood cells.
There are two types of white blood cells: T-cells and B-cells. When T-cells identify a
foreign material or organism, they attack it. When B-cells identify a foreign material,
they secrete special chemicals called antibodies. These antibodies stick on the foreign
material and destroy it. Psoriasis causes abnormal immune system activity of T-cells
in the skin. These T-cells cause the skin to become
inflamed and reproduce excessively.
About 1/3 of all psoriasis cases are inherited. Researchers
are studying large families affected by psoriasis to identify
the genetic factors that cause the disease. People with
psoriasis may notice that symptoms get worse and then
better. Conditions that may cause it to get worse include
climate changes, infection, stress, and dry skin. Medicines
called beta-blockers, used to treat high blood pressure,
and lithium, used to treat depression, can trigger outbreaks
of psoriasis.
Diagnosis & Types
Doctors usually diagnose psoriasis after a carefully examining the skin. However,
diagnosis may be difficult since psoriasis sometimes looks like other skin diseases.
The doctor may need to take a biopsy, a sample of skin. The skin sample is examined
by a pathologist, who views it under a microscope. There are several
forms of psoriasis. The most common form is plaque psoriasis.
In plaque psoriasis, lesions are red at the base and covered by silvery
scales.
Guttate psoriasis. Small lesions appear on the abdomen, chest, back,
limbs, and scalp. Guttate psoriasis is usually triggered by bacterial
infections, such as Streptococcus.
Pustular psoriasis. Blisters of noninfectious pus appear on the skin.
Attacks of pustular psoriasis may be triggered by medication, infection,
emotional stress, or exposure to certain chemicals. Pustular psoriasis
can affect either small or large areas of the body.