Pyoderma Gangrenosum: Differential Diagnoses & Workup

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Pyoderma Gangrenosum: Differential Diagnoses & Workup
Medscape

Author: J Mark Jackson, MD, Assistant Clinical Professor, Department of Internal Medicine, Division of Dermatology, University of Louisville
Coauthor(s): Jeffrey P Callen, MD, Professor of Medicine, Chief, Division of Dermatology, University of Louisville School of Medicine

Updated: Oct 30, 2008

Introduction
Background

Pyoderma gangrenosum (PG) is an uncommon ulcerative cutaneous condition of uncertain etiology. Pyoderma gangrenosum was first described in 1930. It is associated with systemic diseases in at least 50% of patients who are affected. The diagnosis is made by excluding other causes of similar appearing cutaneous ulcerations, including infection, malignancy, vasculitis, collagen vascular diseases, diabetes, and trauma. Ulcerations of pyoderma gangrenosum may occur after trauma or injury to the skin in 30% of patients; this process is termed pathergy.

The 2 primary variants of pyoderma gangrenosum are the classic ulcerative form, usually observed on the legs, and a more superficial variant known as atypical pyoderma gangrenosum that tends to occur on the hands. Patients with pyoderma gangrenosum may have involvement of other organ systems that manifests as sterile neutrophilic abscesses. Culture-negative pulmonary infiltrates are the most common extracutaneous manifestation.1 Other organs systems that may be involved include the heart, the central nervous system, the GI tract, the eyes,2, 3 the liver, the spleen, bones, and lymph nodes. The prognosis of pyoderma gangrenosum is generally good; however, recurrences may occur and residual scarring is common. Therapy of pyoderma gangrenosum involves the use of anti-inflammatory agents, such as corticosteroids, and immunosuppressive agents.
Pathophysiology

The pathophysiology of pyoderma gangrenosum is poorly understood, but dysregulation of the immune system, specifically altered neutrophil chemotaxis, is believed to be involved.
Frequency
United States

Pyoderma gangrenosum occurs in about 1 person per 100,000 people each year.
Mortality/Morbidity

Death from pyoderma gangrenosum is rare, but it may occur due to an associated disease or as the result of therapy. Pain is a usual complaint of patients and may require narcotics. Pathergy, or the development of pyoderma gangrenosum – like lesions at the site of skin trauma, may create problems with wound healing, especially after surgical procedures.
Race

No racial predilection is apparent.
Sex

Pyoderma gangrenosum affects both sexes. A slight female predominance may exist.
Age

All ages may be affected, but pyoderma gangrenosum predominantly occurs in the fourth and fifth decades of life. Children may be affected, but they account for only 3-4% of the total number of cases. Pyoderma gangrenosum may affect children and adolescents. Nothing is clinically distinctive about these patients other than their age.4
Clinical
History

* Patients with pyoderma gangrenosum usually describe the initial lesion as a bite reaction, with a small, red papule or pustule changing into a larger ulcerative lesion. Often, patients give a history of a brown recluse or other spider bite, but they have no evidence that a spider actually caused the initial event.
* Pain is the predominant historical complaint.
* Arthralgias and malaise may often be present.
* A complete history should be taken with special focus on the organ systems listed below to determine any underlying systemic disease. Systemic illnesses are seen in 50% of patients with pyoderma gangrenosum and may occur prior to, concurrently or following the diagnosis.
o Commonly associated diseases include inflammatory bowel disease, either ulcerative colitis or regional enteritis/Crohn disease, and a polyarthritis that is usually symmetric and may be either seronegative or seropositive; and hematologic diseases/disorders, such as leukemia or preleukemic states, predominantly myelocytic in nature or monoclonal gammopathies (primarily immunoglobulin A [IgA]).
o Less common associated diseases include other forms of arthritis, such as psoriatic arthritis, osteoarthritis, or spondyloarthropathy; hepatic diseases, including hepatitis and primary biliary cirrhosis; myelomas (IgA type predominantly); and immunologic diseases, such as lupus erythematosus and Sjögren syndrome.

Physical

* Two main variants of pyoderma gangrenosum exist: classic and atypical. Several other variants may exist.
o Classic pyoderma gangrenosum is characterized by a deep ulceration with a violaceous border that overhangs the ulcer bed. These lesions of pyoderma gangrenosum most commonly occur on the legs, but they may occur anywhere on the body (see Media File 1).
o Atypical pyoderma gangrenosum has a vesiculopustular "juicy" component. This is usually only at the border, is erosive or superficially ulcerated, and most often occurs on the dorsal surface of the hands, the extensor parts of the forearms, or the face (see Media File 2).
o Classic pyoderma gangrenosum may occur around stoma sites; this type is known as peristomal pyoderma gangrenosum. This form is often mistaken for a wound infection or irritation from the appliance (see Media File 3).
o Pyoderma gangrenosum may occur on the genitalia; this form is termed vulvar or penile pyoderma gangrenosum. This variant must be differentiated from sexually transmitted diseases.5
o An intraoral form of the disease, known as pyostomatitis vegetans, has been reported and occurs primarily in patients with inflammatory bowel disease.
o Extracutaneous neutrophilic disease may be evident upon ocular examination and has also been reported in the lungs, liver, and bones.

Causes

No specific causes of pyoderma gangrenosum have been identified, but trauma to the skin in patients with pyoderma gangrenosum may induce new lesions. This is called pathergy.

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Differential Diagnoses
Acute Febrile Neutrophilic Dermatosis
Hypersensitivity Vasculitis (Leukocytoclastic Vasculitis)
Aphthous Stomatitis
Impetigo
Behcet Disease
Insect Bites
Chancroid
Sporotrichosis
Churg-Strauss Syndrome (Allergic Granulomatosis)
Squamous Cell Carcinoma
Ecthyma
Venous Insufficiency
Ecthyma Gangrenosum
Verrucous Carcinoma
Herpes Simplex
Wegener Granulomatosis

Other Problems to Be Considered

Antiphospholipid antibody syndrome
Anthrax
Arterial insufficiency
Acute febrile neutrophilic dermatosis (Sweet syndrome)
Blastomycosis
Factitial disease
Traumatic ulceration
Tuberculosis gumma
Workup
Laboratory Studies

* Routine blood work to evaluate for an underlying systemic illness in persons with pyoderma gangrenosum (PG) includes a CBC count; a comprehensive chemistry profile, including a liver function test; and a urinalysis.
* A hepatitis profile should be performed to rule out hepatitis.
* Serum and/or urine protein electrophoresis, peripheral smear, and bone marrow aspiration should be performed if indicated to evaluate for hematologic malignancies.
* Other serum studies include a Venereal Disease Research Laboratory (VDRL) test, antineutrophil cytoplasmic antibody test, partial thromboplastin time test, and antiphospholipid antibody test to rule out Wegener granulomatosis, vasculitis, and antiphospholipid antibody syndrome. Serum protein electrophoresis is helpful to determine if a monoclonal gammopathy is present. If present, it is often of the IgA subtype.
* Cultures of the ulcer/erosion for bacteria, fungi, atypical mycobacteria, and viruses are needed. The exact cultures to be performed depend on the individual situation. The cultures should be held for 6 weeks because some of the potential agents may take that long to grow in culture.

Imaging Studies

* Chest radiography may be performed.
* Colonoscopy or other tests to exclude associated inflammatory bowel disease or ulcerative colitis may be useful in patients with symptoms. The evaluation of patients with pyoderma gangrenosum and no symptoms of bowel disease is still uncertain.
* Angiography or Doppler studies may be performed in patients suspected of having arterial or venous insufficiency.

Other Tests

* The following tests may be performed:
o Flexible sigmoidoscopy or colonoscopy in selected patients
o Bone marrow aspiration or biopsy in selected patients
o Culture of the ulceration and possibly of the biopsy material

Procedures

* A skin biopsy should be performed.

Histologic Findings

The histopathologic findings in pyoderma gangrenosum are not specific. However, a biopsy is suggested in almost all instances because it is useful in the exclusion of other diseases. Microscopic features include massive neutrophilic infiltration, hemorrhage, and necrosis of the overlying epidermis. Histologically, this finding may simulate an abscess or cellulitis. Neutrophils are often around and within the vessel walls, but the full picture of vasculitis is generally absent. In early disease, a mixed cell infiltrate may be present. Late in the process, granulation tissue may be present, but granuloma formation is generally believed to be incompatible with the diagnosis of pyoderma gangrenosum.

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