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A 32-year-old man was diagnosed with Crohn disease 10 years prior to his visit for these nonhealing leg ulcers (Figure 183-1). The patient experienced minor trauma to his lower leg 1 year ago and these ulcers developed (pathergy). Multiple treatments have been tried with partial success, but the ulcers persist.

FIGURE 183-1

Classic pyoderma gangrenosum on the leg of a 32-year-old man with Crohn disease. This ulcer started with minor trauma (pathergy) and has been there for 1 year. (Reproduced with permission from Richard P. Usatine, MD.)


Pyoderma gangrenosum (PG) is an uncommon ulcerative disease of the skin of unknown origin. It is a type of neutrophilic dermatosis—an inflammatory neutrophilic dermatosis—and is frequently associated with other systemic diseases.1


  • PG occurs in approximately 1 person per 100,000 each year.2

  • A published case series reported a mean age between 50 and 63 years.3 All ages may be affected.

  • No racial predilection is apparent.

  • A slight female predominance may exist.


  • Etiology is poorly understood. It has no infectious etiology and no tissue-related vascular gangrene.1

  • Pathergy (initiation at the site of trauma or injury) is a common process, and it is estimated that 30% of patients with PG experienced pathergy.2

  • Associated systemic diseases such as inflammatory bowel disease (IBD), hematologic malignancy, and rheumatoid arthritis and solid tumors have been documented in 33% to 75% of patients. The rest are idiopathic.1,4

  • It associated with ulcerative colitis (5%–12%) and to a lesser extent Crohn disease (1%–2%) (Figures 183-2 and 183-3).1

  • PG is thought to be autoimmune resulting from defects in cell-mediated immunity, neutrophil and monocyte function, and humoral immunity. Biopsies usually show a polymorphonuclear cell infiltrate with features of ulceration, infarction, and abscess formation.1

  • PG also can be induced by drugs such as isotretinoin, propylthiouracil, granulocyte colony-stimulating factor, sunitinib, and cocaine.5

FIGURE 183-2

Friable inflamed mucosa of the colon in Crohn disease. (Reproduced with permission from Shashi Mittal, MD.)

FIGURE 183-3

Classic pyoderma gangrenosum on the leg of a 35-year-old woman with Crohn disease. This ulcer started with minor trauma (pathergy) and has been there for 2 years. (Reproduced with permission from Richard P. Usatine, MD.)


  • Ulcerative colitis4,6.

  • Crohn disease.

  • Polyarthritis (seronegative or seropositive).

  • Hematologic diseases/disorders such as leukemia (predominantly myelocytic).

  • Monoclonal gammopathies (primarily immunoglobulin A).

  • Psoriatic arthritis and rheumatoid arthritis (Figure 183-4).

  • Hepatic diseases (hepatitis and primary biliary cirrhosis).

  • Immunologic ...

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