Pyoderma Gangrenosum Workup

Updated: Mar 09, 2020
  • Author: J Mark Jackson, MD; Chief Editor: William D James, MD  more...
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Approach Considerations

Pyoderma gangrenosum is a diagnosis of exclusion as no specific criteria have been determined to confirm the diagnosis. All other potential causes of similar lesions must be excluded prior to making the diagnosis.

Routine blood work to evaluate for an underlying systemic illness in persons with pyoderma gangrenosum includes a complete blood count (CBC); a comprehensive chemistry profile, including a liver function test; and a urinalysis. In addition, a hepatitis profile should be performed.

Serum and/or urine protein electrophoresis, peripheral smear, and bone marrow aspiration or biopsy should be performed, if indicated, to evaluate for hematologic malignancies.

Other serum studies include a Venereal Disease Research Laboratory (VDRL) test, an antineutrophil cytoplasmic antibody test, a partial thromboplastin time test, and an antiphospholipid antibody test, all of which can help to rule out the following diseases: granulomatosis with polyangiitis (formerly known as Wegener granulomatosis), vasculitis, and antiphospholipid antibody syndrome.

Anti–Saccharomyces cerevisiae antibodies (IgG and IgA) occur in patients with inflammatory bowel disease and might be of value for the identification of an associated disease when there are no bowel symptoms. In addition, perinuclear antineutrophil cytoplasmic antibodies (p-ANCA) occur in some patients with  inflammatory bowel disease. c-ANCA should be tested, but is not associated with inflammatory bowel disease and, in an appropriate patient, might lead to a diagnosis of granulomatous polyangiitis. Fecal calprotectin is another test to consider when assessing a patient with pyoderma gangrenosum for associated inflammatory bowel disease.

Serum immunofixation electrophoresis is helpful to determine if a monoclonal gammopathy is present. If it is, it is most frequently an IgA subtype. Myeloma, however, is a rare association.


Tissue 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. Angiography or Doppler studies may be carried out in patients suspected of having arterial or venous insufficiency.


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.


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, such as infections and malignancy. Microscopic features include massive neutrophilic infiltration, hemorrhage, and necrosis of the overlying epidermis. Histologically, this finding may simulate an abscess or cellulitis, although no organisms are seen and cultures are generally negative or only demonstrate typical skin flora. 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.