Crohn's disease is a chronic inflammatory bowel disease. The disease is characterized by acute exacerbations with diarrhea, abdominal pain, fever, anorexia, intestinal bleeding, and weight loss. Immune-mediated diseases that are frequently associated with Crohn's disease include arthritis, ankylosing spondylitis, sacroiliitis, episcleritis, uveitis, and skin lesions, such as erythema nodosum and pyoderma gangrenosum. The authors present the case of a 22-year-old female patient that was admitted to their hospital due to diarrhea, fever, arthralgias, and diffuse erythematous papules and plaques with vesicles and pustules affecting the patient's face, lips, arms, trunk, and legs. Six months prior to onset, the patient was diagnosed with terminal ileitis and Crohn's disease of the sigmoid colon. Treatment with mesalazine and budesonide had been introduced. In the diagnostic procedure, a skin biopsy was taken from the patient. Histology confirmed dense infiltration of neutrophilic polymorphonuclear leukocytes, or Sweet's syndrome. This condition is a rare manifestation of chronic inflammatory bowel diseases such as Crohn's disease and ulcerative colitis. This syndrome is thought to be a hypersensitivity reaction and may be associated with various inflammatory, infectious, or neoplastic diseases. The patient was treated with high doses of methylprednisolone (60 mg IV), which resulted in rapid improvement of Crohn's disease and skin lesions.