Pyoderma Gangrenosum

Pyoderma gangrenosum (PG) is an uncommon condition of uncertain origin.
It is a unique, painful, inflammatory, ulcerative process of the skin.
PG is often seen in association with certain systemic diseases including ulcerative colitis, regional enteritis, rheumatoid arthritis, symmetrical polyarthritis that may be either seronegative or seropositive, or monoclonal gammopathies, and leukemia.
Patients often describe the initial lesion as a “pimple” or bite reaction, with a small, red papule or pustule rapidly changing into a larger, ulcerative lesion. Often, they give a history of a spider bite, but generally they have not seen or documented the presence of a spider, nor do they have any evidence that a spider actually caused the initial lesion.

Lesions are characterized by a rapidly expanding, painful, deep skin ulcer with a violaceous border that overhangs the ulcer bed.
Skin ulcers are 2 to 10 cm in diameter.
An undermined border can be demonstrated by a probe that can be placed under the overhanging edge of the lesion.
Lesions may be multiple.
Lesions typically heal with so-called cribiform scarring (Fig. 34.44).
PG is usually self-limited and spontaneous healing may occur.
Patients may have an associated oligoarticular arthritis.
Ulcerations of PG occur after trauma or injury to the skin in some patients; this process is termed pathergy.
PG is most commonly found on the lower extremities (shins and ankles), around stoma site (peristomal pyoderma gangrenosum), but lesions may occur anywhere on the body (Fig. 34.45).

Generally made on a clinical basis, after exclusion of other causes of similar-appearing cutaneous ulcerations including infection, stasis ulcers, malignant disease, vasculitis, collagen vascular diseases, diabetes, and trauma.

Laboratory Evaluation

Skin biopsy of the edge of the ulcer may be performed to rule out other causes of skin ulcers, however, the pathologic findings for PG are nonspecific.
Bacterial, fungal, and viral cultures of the ulcer are performed if clinically indicated.
Workup for systemic disease should include complete blood count with differential, erythrocyte sedimentation rate, ANA, Venereal Disease Research Laboratory test, rheumatoid factor, and a chest radiograph.
Serum or urine protein electrophoresis, peripheral smear, and bone marrow aspirate are performed, if indicated, to evaluate for hematologic malignant diseases.
A gastrointestinal series for inflammatory bowel disease should be done if clinically indicated.

Differential Diagnosis

Cutaneous Malignant Diseases

Infectious Processes

Inflammatory Processes and Vasculitis

Management

The treatment of underlying associated diseases does not necessarily promote the healing of PG.

Topical and Intralesional Therapy

Local compresses, antiseptic washes, and topical antibiotics may be useful.
Superpotent topical corticosteroids, cromolyn sodium 2% solution, nitrogen mustard, and 5-aminosalicyclic acid may be tried.
Intralesional steroid injections (triamcinolone acetonide, 10 mg/mL) are administered into the edge of the ulcer.

Systemic Therapy

Oral steroids for several weeks to months (starting at 60 to 80 mg prednisone daily and tapering the steroid slowly). Systemic steroids may be given alone or in combination with dapsone, azathioprine, or chlorambucil. In patients with steroid-resistant PG, oral cyclosporine has been shown to be effective.
The following drugs have also met with some success: mycophenolate mofetil (CellCept), tacrolimus, cyclophosphamide, thalidomide, and nicotine chewing gum.
Intravenous therapy can be administered using pulsed methylprednisolone, pulsed cyclophosphamide, or human immunoglobulin.
Surgical grafting and microvascular free flaps are best reserved for after the disease has become inactive.

Other Therapies

Hyperbaric oxygen.
Biologics such as etanercept (Enbrel), adalimumab (Humira), and infliximab (Remicade) may prove useful.

Point to Remember

Surgical debridement of the lesions of PG should be avoided, if possible, because of the pathergy that may occur with surgical manipulation or grafting. This can result in further wound enlargement.