Chapter 183: Pyoderma Gangrenosum

PATIENT STORY

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.

INTRODUCTION

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

EPIDEMIOLOGY

• 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 AND PATHOPHYSIOLOGY

• 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

RISK FACTORS

• Ulcerative colitis^4,6.

• 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 ...