Pyoderma gangrenosum: a systematic review.

Pyoderma gangrenosum (PG) is a rare, chronic neutrophilic dermatosis of unknown etiology. The world wide incidence is estimated to be around 3-10 cases per million population per year. In 50-70% of cases inflammatory bowel diseases, hematological malignancies or rheumatologic disorders are associated to PG. Although the etiology is uncertain, the dysregulation of the immune system appears to be implied. Pathergy is the most important triggering factor of PG. Indeed, 20-30% of patients report the onset of PG following trivial trauma. Four main variants of PG have been described, namely classic, pustular, bullous, and vegetative forms. The classic form of PG is characterized by ulcers with a raised, undermined, inflammatory border. Intense pain is generally associated to PG. The diagnosis is mainly clinical and of exclusion. The differential diagnosis should take into account infections, vascular disorders and malignancies. The clinical course can be explosive and rapidly progressive or indolent and gradually progressive. Often patients develop only one episode and the overall prognosis is good but extremely influenced by the underlying disorders. Local therapy, mainly with topic steroids is used for mild to moderate lesions. For severe forms of PG a systemic therapy with glucocorticoids and/or other drugs such as tacrolimus, cyclosporine, etc. is needed. This paper is a systematic review of literature on PG.