A 19-year-old man with nodulocystic acne on baseline was treated with isotretinoin therapy. After 1 month on the medication, he developed pyoderma gangrenosum on his pubis area, arms and legs, and pathergy on a puncture site. Possible underlying diseases were excluded. The patient was started on steroids (prednisone 1 mg/kg/d) and isotretinoin therapy was withdrawn. Later the prednisone was tapered and dapsone 100 mg/daily was initiated. After 10 months of follow-up all lesions had healed and no underlying diseases developed.