What is the treatment approach for pyoderma gangrenosum?

Pyoderma Gangrenosum: Signs, Symptoms, and Workup

Clinical Presentation

Pyoderma gangrenosum presents as rapidly developing, painful skin ulcers with characteristic undermined violaceous borders and peripheral erythema, most commonly on the lower extremities. 1

Key Clinical Features

• Initial lesion: Sterile pustules that rapidly progress within 24-48 hours to painful ulcers of variable depth and size 2, 3
• Ulcer characteristics: Deep excavating ulcerations with purulent material that is sterile on culture (unless secondary infection has occurred), with undermined violaceous borders 4, 1
• Location: Legs are most frequently affected, particularly the shins, though any skin surface or mucous membranes can be involved 2, 3
• Peristomal involvement: Lesions commonly occur adjacent to postsurgical stomas 2
• Pathergy phenomenon: 20-30% of cases are preceded by trauma, meaning lesions develop at sites of injury or surgical intervention 2, 5

Associated Symptoms

• Pain: Lesions are characteristically painful, distinguishing them from many other ulcerative conditions 3, 1
• Rapid progression: Ulcers can expand quickly over days, causing significant morbidity 6, 1

Diagnostic Workup

Pyoderma gangrenosum is primarily a diagnosis of exclusion requiring clinical assessment, biopsy to rule out mimics, and investigation for underlying systemic diseases. 4

Clinical Diagnosis

• Pattern recognition: Diagnosis is typically made clinically based on the characteristic appearance of rapidly developing painful ulcers with undermined violaceous borders 4
• High misdiagnosis rate: Be aware that misdiagnosis occurs in a substantial percentage of cases due to variable presentation 7, 4

Biopsy Approach

• When to biopsy: In atypical cases, biopsy from the periphery of the lesion helps exclude other disorders 2, 4
• Histopathology findings: Biopsy findings are non-specific but can rule out infections, vasculitis, and malignancies 5, 4
• Neutrophilic infiltrate: Expect to see neutrophilic dermatosis pattern without specific diagnostic features 3, 8

Critical Differential Diagnoses to Exclude

• Ecthyma gangrenosum: Bacterial cutaneous vasculitis (typically Pseudomonas) presenting as painless erythematous papules progressing to painful necrotic lesions within 24 hours—requires antibiotics, not immunosuppression 7
• Necrotizing vasculitis: Requires tissue diagnosis to differentiate 4
• Arterial or venous insufficiency ulceration: Consider vascular studies if location and patient risk factors suggest 4
• Infections: Culture wound material to confirm sterility 4, 3
• Malignancy: Particularly in atypical presentations or treatment-resistant cases 4

Screening for Associated Conditions

50-70% of pyoderma gangrenosum cases are associated with underlying systemic disorders, making comprehensive screening essential. 5

• Inflammatory bowel disease: Most common association, occurring in 0.6-2.1% of ulcerative colitis patients 5

  • Obtain colonoscopy if gastrointestinal symptoms present or no prior IBD diagnosis 5
  • Note that IBD activity may parallel pyoderma gangrenosum or run an independent course 5

• Hematological malignancies: Screen with complete blood count, peripheral smear, and consider bone marrow evaluation if cytopenias or abnormal cells present 5, 3

• Rheumatologic disorders: Particularly rheumatoid arthritis—obtain rheumatoid factor, anti-CCP antibodies, inflammatory markers 5, 3

• Other systemic inflammatory conditions: Consider age-appropriate malignancy screening 5

Laboratory Evaluation

• Wound cultures: To confirm sterility and rule out secondary infection 4, 3
• Inflammatory markers: ESR, CRP to assess systemic inflammation 8
• Complete blood count: Screen for hematologic abnormalities 3
• Comprehensive metabolic panel: Baseline before initiating immunosuppressive therapy 8

Common Pitfalls to Avoid

• Surgical debridement during active disease: Avoid sharp debridement as pathergy will worsen lesions; surgical intervention should be reserved for after disease control 7, 6
• Treating as infection: Do not delay immunosuppression while pursuing prolonged antibiotic trials for sterile ulcers 7
• Missing underlying disease: Failure to screen for associated conditions, particularly IBD, which may present after pyoderma gangrenosum in some cases 5
• Inadequate biopsy: If performing biopsy, sample from the periphery rather than the necrotic center for better diagnostic yield 2, 4

Prognosis and Recurrence

• High recurrence rate: More than 25% of cases recur, often in the same location as the initial episode 7, 5
• Variable course: Disease can be mild or malignant, chronic or relapsing with remarkable morbidity 3
• Peak incidence: Ages 20-50 years, with women more commonly affected than men 3