(See also Overview of Hypersensitivity and Reactive Skin Disorders Overview of Hypersensitivity and Reactive Skin Disorders The immune system plays a vital role in maintaining the health of all the tissues of the body. The immune system reacts to invaders, such as microorganisms, foreign substances, or cancer cells... read more .)
The cause is not known, but this disorder can develop after an injury or in people with certain disorders.
This disorder begins as small bumps or blisters that become open sores.
The diagnosis is usually based on the appearance of the sores.
Treatment includes dressings, creams, and drugs.
The cause of pyoderma gangrenosum is unknown, but people who have pyoderma gangrenosum tend to have certain underlying disorders, including inflammatory bowel disease Overview of Inflammatory Bowel Disease (IBD) In inflammatory bowel diseases, the intestine (bowel) becomes inflamed, often causing recurring abdominal pain and diarrhea. The two primary types of inflammatory bowel disease (IBD) are Crohn... read more , arthritis, cancers, and blood disorders.
In pyoderma gangrenosum, the immune system seems to be reacting to the skin itself. Unlike many inflammatory skin conditions that are caused by lymphocytes Lymphocytes One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more 
(a type of white blood cell White blood cells The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more ), antibodies Antibodies One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more (proteins), or both, pyoderma gangrenosum involves abnormal function of another type of white blood cell called neutrophils Neutrophils One of the body's lines of defense (immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more (see Overview of the Immune System Overview of the Immune System The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more ).
Pyoderma gangrenosum typically affects people who are 25 to 55 years old. Pyoderma gangrenosum can develop on areas of skin that have recently been injured or operated on. Thus, areas affected by pyoderma gangrenosum often worsen if they are biopsied (a sample of skin is removed for examination) or debrided (dead tissue is removed to clean the affected area).
Symptoms of Pyoderma Gangrenosum
Most often, pyoderma gangrenosum begins as a red bump that may resemble a pimple or an insect bite. Less often, it begins as a blister. The bump or blister then becomes an open, painful sore (ulcer) that expands rapidly. The sores have a raised border that is dusky or purple. The sores can grow together to form larger sores. People often are left with scars after ulcers heal. People commonly have fever and a general feeling of illness (malaise).
Pyoderma gangrenosum can also develop at other locations, such as in the abdominal wall around a colostomy or ileostomy opening in people who have inflammatory bowel disease, or on the genitals. In some people with pyoderma gangrenosum, areas other than the skin, such as the bones, lungs, heart, liver, or muscles, are affected.
Diagnosis of Pyoderma Gangrenosum
A doctor's evaluation
Doctors diagnose pyoderma gangrenosum by the appearance of the sores and by ruling out other diseases that cause sores to form on the skin. The diagnosis of pyoderma gangrenosum is strongly suggested if the sores worsen after they are debrided.
A sample of skin may need to be removed and examined under a microscope (called a skin biopsy Biopsy Doctors can identify many skin disorders simply by looking at the skin. A full skin examination includes examination of the scalp, nails, and mucous membranes. Sometimes the doctor uses a hand-held... read more 
), even though this procedure might worsen the problem temporarily.
Treatment of Pyoderma Gangrenosum
Dressings
Corticosteroids or tacrolimus applied to the skin
Sometimes drugs to suppress the immune system
Dressings that protect the skin from drying are applied to help heal the sores.
Potent corticosteroid creams or tacrolimus can be directly applied to sores that are new and not deep. Prednisone taken by mouth is given to people severely affected by the disease.
Drugs that suppress the immune system, such as infliximab, adalimumab, and etanercept, are helpful, particularly for people who have inflammatory bowel disease Overview of Inflammatory Bowel Disease (IBD) In inflammatory bowel diseases, the intestine (bowel) becomes inflamed, often causing recurring abdominal pain and diarrhea. The two primary types of inflammatory bowel disease (IBD) are Crohn... read more .
Cyclosporine can be very effective, particularly for people whose disease is progressing rapidly. Dapsone, azathioprine, cyclophosphamide, methotrexate, clofazimine, thalidomide, mycophenolate mofetil, and minocycline are other treatment options.
Surgical treatments are typically not done because they may worsen the sores.
