History. The most common history for patients with pyoderma is of a small lesion thought to be a bite or scratch that rapidly grew in size, or following a medical procedure such as surgery or even something as seemingly innocuous as a needle biopsy, as in case 2 (Figure 2) and case 3 (Figure 3A-3D).
Patient population. Some patients with pyoderma have known inflammatory conditions such as inflammatory bowel disease (IBD) (ie, Crohn’s disease or ulcerative colitis) or other diseases such as lupus, leukemia, or hepatic disease. The percentage of patients with pyoderma who also have IBD was originally quoted at around 50%, but subsequent reviews have seen fewer percentages of pyoderma patients with associated IBD.2 Several explanations have been given for this apparent increase of isolated pyoderma over time, such as many of the original series were from tertiary referral hospitals specializing in IBD, or clinicians have become more comfortable over time in diagnosing isolated pyoderma.2
Presentation. Pyoderma lesions may present de novo or following minor trauma, a bite, or surgery.3 Peristomal pyoderma is essentially a postsurgical presentation that has been recognized since 1984.4 Peristomal pyoderma is especially common in patients with IBD following surgery and creation of a stoma. While peristomal pyoderma may be more readily recognized because of its location, it may be misdiagnosed from irritation of the appliance or an infection.
Nonperistomal pyoderma can present anywhere on the body, and case 4 (Figures 4A-4C) shows a case of pyoderma presenting on the hands. While there are other generally traumatic or infectious causes of hand wounds, whenever unusual lesions present on the hands—especially if there are multiple lesions—it should trigger immediate consideration of pyoderma.
Appearance and culture results of lesions. The classic pyoderma lesion is a full-thickness ulcer with bluish purple undermining borders (Figures 4A, 4C). There is no definitive histologic feature, but histologic changes that support the diagnosis are neutrophilic infiltration of the dermis and cutis.
Despite the fact the wounds often have considerable white cell debris that look like pus in the undermining areas, cultures have most often shown no growth in the author’s experience. Positive cultures certainly do not rule out pyoderma; however, pyoderma wounds can become colonized or infected and have positive cultures, especially if they have been open for a prolonged period.
Role of biopsy. Biopsy is used in potential pyoderma cases to rule out other causes for the ulcers. Weenig et al5 described a misdiagnosis rate of about 10% in their series from the Mayo Clinic and from literature review.5 They concluded biopsy is always warranted because the treatment of pyoderma will often embark a patient on a course of systemic steroids. They classified the nonpyoderma cases that were misdiagnosed as pyoderma into the following groups: vascular or occlusive disease, vasculitis, malignant process, primary infection, drug induced or exogenous tissue injury, and other inflammatory conditions.
Weenig and coauthors5 also noted that venous stasis wounds are the most common lower extremity wounds but usually do not look like pyoderma. Venous stasis ulcers generally are not as painful and have associated hemosiderin deposition. Vasculitic ulcers can be difficult to distinguish from pyoderma, and they also often respond to steroids. In addition, they noted that antiphospholipid antibody syndrome is “a highly problematic simulator of pyoderma” due to its appearance and response to steroids, but that the lupus anticoagulant was nearly always positive with antiphospholipid syndrome and ulcers.
Case 5. This case shows a patient with vasculitis due to antiphospholipid antibody syndrome, which can be similar to pyoderma. The presentation of a painful wound is somewhat similar to pyoderma, but the purpura were more widespread (at least during a time of the vasculitis flare up) than typically seen in pyoderma. The prednisone had to be increased when the vasculitis flared up, and an extreme halo of purple was noted. Vaculitis is similar to pyoderma in its response to steroids and also in the potential benefit of using human allograft (Figures 5A-5E).
Role of biopsy. Clinical judgement makes the diagnosis of pyoderma, not biopsy, so in this author’s practice, clinicians have not felt biopsy is mandatory in diagnosing and treating every case of pyoderma, but that it should certainly be employed liberally. Decisions on when to biopsy are made on a case-by-case basis. Table 1 lists the factors considered when deciding whether or not to biopsy; when more left-column factors are present, the more comfortable avoiding biopsy becomes (Table 1).
One reason clinicians may be hesitant to biopsy lesions thought to be pyoderma is to avoid the possibility of potentiating pathergy and have the wounds worsen. In the author’s experience, this risk can be avoided by having the patient on systemic steroids starting before the biopsy and continuing until pyoderma is ruled out.