What are the causes of pyoderma gangrenosum?

Causes of Pyoderma Gangrenosum

Pyoderma gangrenosum is most commonly associated with inflammatory bowel disease, particularly ulcerative colitis, as well as hematological malignancies, rheumatologic disorders, and other systemic inflammatory conditions. 1

Primary Associated Conditions

• Inflammatory Bowel Disease (IBD)

  • Occurs in 0.6-2.1% of ulcerative colitis patients, with a higher frequency than in Crohn's disease 1
  • May parallel IBD activity or run an independent course 1

• Hematological Malignancies

  • Various blood cancers can trigger pyoderma gangrenosum 2, 3

• Rheumatologic Disorders

  • Including rheumatoid arthritis and other autoimmune conditions 2, 4

• Other Systemic Conditions

  • Chronic active hepatitis 5
  • Paraproteinemias 3
  • Diabetes mellitus 5

Pathophysiological Mechanisms

• Abnormal Neutrophil Function

  • Pyoderma gangrenosum is hypothesized to involve dysregulation of neutrophils 1
  • Classified as a neutrophilic dermatosis 2

• Impaired Cellular Immunity

  • Immune system dysregulation appears to be implicated in the development of lesions 1, 3

• Pathergy Phenomenon

  • Trauma can trigger lesion development in 20-30% of cases 1, 2
  • Lesions are often preceded by trauma, which explains post-surgical and peristomal occurrences 1

Clinical Patterns and Associations

• Disease Association Rate

  • 50-70% of pyoderma gangrenosum cases are associated with underlying systemic disorders 2, 3
  • In some cases, pyoderma gangrenosum may precede the diagnosis of the underlying condition, particularly IBD 4

• Recurrence Pattern

  • High recurrence rate of more than 25% following successful treatment 1
  • Recurrences often occur in the same location as the initial episode 1

Diagnostic Considerations

• Diagnosis of Exclusion

  • Pyoderma gangrenosum is diagnosed after ruling out other possible skin diseases 6
  • Differential diagnosis includes infections, vascular disorders, and malignancies 2

• Biopsy Findings

  • Findings are non-specific but can help exclude other disorders 6
  • Biopsy from the periphery of the lesion is recommended when performed 1

Treatment Implications

• Therapeutic Approach

  • Treatment should target both the pyoderma gangrenosum and any underlying condition 7
  • Systemic corticosteroids are traditionally first-line treatment 7
  • Anti-TNF agents like infliximab and adalimumab are effective second-line options 7

• Disease Course

  • Can be explosive and rapidly progressive or indolent and gradually progressive 2
  • Prognosis is generally good but influenced by underlying disorders 2, 8

Understanding the underlying causes of pyoderma gangrenosum is essential for proper management and treatment of this debilitating skin condition.