Pyostomatitis vegetans (PV) is a rare condition characterized by pustules that affect the oral mucosa. It is a highly specific marker for inflammatory bowel disease and its correct recognition may lead to the diagnosis of ulcerative colitis or Crohn's disease. Thus, a presumptive diagnosis of PV should suggest a complete gastrointestinal investigation. PV pathogenesis is as yet unknown, although immunological and microbial factors have been suggested as possible aetiological factors. Pyostomatitis vegetans is characterized by erythematous, thickened oral mucosa with multiple pustules and superficial erosions. A peripheral eosinophilia has been observed in most cases reported. Histology shows epithelial acanthosis and superficial ulceration with intraepithelial and / or subepithelial abscesses containing large numbers of eosinophils. The underlying connective tissue exhibits neutrophil and eosinophil infiltration, with miliary abscesses in some cases. Treatment of PV focuses on control of the underlying disease.