Pyoderma vegetans (PV) is a rare disorder clinically characterized by large verrucous plaques with elevated borders and multiple pustules. Pyoderma vegetans is an eruption of multiple pustular ulcerations; it may have a bacterial etiology similar to chancriform pyoderma. [1, 2, 3, 4]
Hallopeau first characterized this process in 1898.  Although its etiology is unknown, this disease has been attributed to bacterial infection in an individual who is immunocompromised  ; more recent reports support this theory. [2, 6, 7] Pyoderma vegetans has been associated with ulcerative colitis, [8, 9, 10, 11] diffuse T-cell lymphoma,  alcoholism with malnutrition,  HIV infection,  chronic myeloid leukemia (CML),  and lupus nephritis. 
Su et al reported 7 patients with clinically characteristic pyoderma vegetans.  These patients had various conditions that compromised their immune systems; these conditions included pulmonary granuloma, chronic granulocytic leukemia, arthritis treated with azathioprine and prednisone, and seminoma treated with x-ray irradiation, which predisposed them to bacterial infections.  After pyoderma vegetans was diagnosed, 1 patient developed squamous cell carcinoma and colonic carcinoma. Ishibashi described a patient with pyoderma vegetans without any history of an immunocompromising condition. 
The etiology of pyoderma vegetans (PV) is not known, although it is often associated with staphylococcal and streptococcal infections in a patient with an immunosuppressive state or a dysfunction of the immune system. The immunological dysfunction is believed to induce the development of vegetations. In addition to bacterial infections, fungal infections have also been implicated in the context of immunosuppression, as demonstrated by a case of treatment-resistant Trichophyton mentagrophytes –induced tinea manuum resulting in a chronic pyoderma vegetans in a patient with decreased immunoglobulins and impaired phagocytosis. 
Diffuse T-cell lymphoma,  ulcerative colitis,  and HIV infection  have been associated with this condition. A patient was described with pyodermatitis-pyostomatitis vegetans associated with ulcerative colitis who, upon immunofluorescence examination, demonstrated in vivo bound and circulating immunoglobulin G antibasement membrane zone antibodies.  These antibodies reacted with the bullous pemphigoid antigen 230. The presence of circulating autoantibodies to the bullous pemphigoid antigen 230 in this patient was considered an epiphenomenon, resulting from epidermal damage induced by inflammation of the pyodermatitis-pyostomatitis vegetans. Pyoderma vegetans may also be associated with myelodysplastic syndromes. 
Pyoderma vegetans is rare.
With therapy, the prognosis is good, although this may prove untrue in the face of associated medical conditions, such as HIV, diffuse T-cell lymphoma, and CML, which must be properly addressed.
In patients in whom inflammatory bowel disease does not coexist, pyoderma vegetans has a good prognosis with therapy. In contrast, pemphigus vegetans has a poor prognosis without the continuous use of immunosuppressive drugs.