Pyoderma gangrenosum is a rare dermatosis of unknown etiology. It is classified as being a neutrophilic dermatosis,
in which there is inflammatory infiltration consisting primarily of mature polynuclear leukocytes. Its
pathogenesis is multifactorial and is thought to involve neutrophilic dysfunction, inflammatory mediators in
combination with a genetic predisposition for the disease. Neutrophilic infiltration is observed in new lesions,
while necrosis associated with fibrosis and granulomas are seen in chronic lesions, however these findings are
not pathognomonic. Pyoderma gangrenosum can occur at any age. However, it most commonly develops in young
and middle-aged adults predominantly women between the second and fifth decades of life. Grossly, pyoderma
gangrenosum is characterized by skin lesions in the form of rapidly spreading ulcers, with cylindrical edges and
necrotic bottoms. These ulcers are painful and crusted but have undermined borders. Pyoderma gangrenosum
commonly presents with the rapid development of one or more purulent ulcers with undermined borders on
sites of normal or traumatized skin. Pyoderma gangrenosum is often associated with other systemic diseases
such as ulcerative colitis, Crohn’s disease, monoclonal gammopathies, IgG or IgA myelomas and tumors of internal
organs and hematopoietic system diseases, which supports the immunological mechanisms involved in the
pathogenesis of the disease. Of note, neutrophilic infiltration associated with other extracutaneous manifestations
and different systemic disorders can co-exist with pyoderma gangrenosum. Despite the recent development
of immune modulating drugs in the treatment of skin conditions, steroid therapy still plays a pivotal
role. For patients with mild pyoderma gangrenosum, the local application of topical corticosteroids or calcineurin
inhibitors can be sufficient. Systemic therapy is necessary in patients with more extensive disease. The role
of surgery is controversial, as it is associated with the induction of pathergy. The clinical, histopathologic and
laboratory findings in pyoderma gangrenosum are non-specific, and a diagnosis can only be made once other
diagnoses have been excluded.
Bullous Pyoderma Gangrenosum
