Many patients with pyodermatitis will have an inflammatory bowel disease (either Crohn's disease or ulcerative colitis), but not all. Pyodermatitis may appear months or years before there is evidence of the inflammatory bowel disease.
Typical findings:
(1) The patient develops an erythematous papulopustular skin eruption.
(2) Lesions are asymmetrical and become crusted.
(3) The pustules tend to aggregate into vegetating plaques.
(4) Plaques are most often found in the scalp, groin and axillary folds.
Other findings:
(1) concurrent pyostomatitis vegetans may be present
(2) concurrent inflammatory bowel disease-related liver disease may be present
(3) exclusion of other causes (negative bacterial cultures, negative immunofluorescence, etc)
Biopsy of an early lesion shows intraepithelial or subepithelial microabscesses with neutrophils and eosinophils.
