Random Dermatology MCQ - Peristomal complications

A 72-year-old patient with a history of rheumatoid arthritis on adalimumab presents for a routine follow-up 6 months after an ileostomy for Crohn's disease. They report excellent control of their bowel symptoms but have a persistent, painful peristomal skin issue that has failed multiple interventions. Examination reveals a 3 cm area of ulceration with a sharply demarcated, violaceous, and deeply undermined border located at the 3 o'clock position relative to the stoma. The surrounding skin is otherwise intact, and the stoma appliance appears well-fitted with no evidence of leakage. Past failed treatments include multiple appliance changes (including a trial of a convex system), nystatin powder, and a high-potency topical corticosteroid. What is the most likely diagnosis?

A. Allergic contact dermatitis to the stoma flange
B. Irritant contact dermatitis from enzymatic damage
C. Pyoderma gangrenosum
D. Pressure ulcer from an ill-fitting appliance
E. Locally invasive recurrent Crohn's disease

Correct Answer: C. Pyoderma gangrenosum

Answer & Explanation

Explanation:

This question is difficult because it requires distinguishing between several plausible causes of a refractory peristomal ulcer, all of which can occur in this patient population. The key lies in recognizing the specific clinical features that point away from the other options and toward pyoderma gangrenosum (PG).

• Why C is correct: The description of the ulcer is classic for PG: a painful ulcer with a characteristic violaceous, undermined border. PG is a well-known, neutrophilic dermatosis strongly associated with both inflammatory bowel disease (Crohn's) and rheumatoid arthritis. Its course is often refractory to standard wound care and topical steroids and requires systemic immunosuppression. The location is typical for PG, which can arise at sites of trauma (pathergy), such as a stoma site.

• Why the other options are incorrect:

  • A. Allergic contact dermatitis: This typically presents as a pruritic, eczematous, vesicular plaque that corresponds to the pattern of allergen contact (e.g., the entire area under the flange). It would not typically present as a solitary, deeply undermined ulcer. The failure of multiple appliance changes makes this less likely.

  • B. Irritant contact dermatitis: This is the most common peristomal problem, but it presents as a diffuse, moist, "beefy red" erythema in the area of effluent contact, not a solitary, well-defined, undermined ulcer. A well-fitted appliance with no leakage argues strongly against this.

  • D. Pressure ulcer from an ill-fitting appliance: This is a strong distractor. Pressure ulcers can occur from a rigid flange. However, they typically present with necrosis, eschar formation, and a more regular, non-undermined border. The specific violaceous and undermined edge is the hallmark of PG, not pressure.

  • E. Locally invasive recurrent Crohn's disease: Cutaneous Crohn's disease can present with ulcers, sinus tracts, and nodules. However, the violaceous, undermined border is far more specific for PG. While Crohn's and PG can coexist, the described morphology is pathognomonic for the latter. The patient's systemic disease is well-controlled on adalimumab (which can also treat PG), but PG can be refractory and break through therapy.

Key Associations and Nuances

• Pathergy in PG: The phenomenon where PG lesions develop at sites of minor trauma, such as a surgical stoma site, is a critical diagnostic clue.

• Diagnosis: PG is a clinical diagnosis. A biopsy is often performed but is not pathognomonic; it typically shows a dense neutrophilic infiltrate and is primarily used to rule out other causes like infection or vasculitis. The biopsy can worsen the lesion due to pathergy.

• Management Implications: This is where the difficulty lies. Standard peristomal care (addressing leakage, infection, allergy) has failed. The correct management pathway is systemic immunosuppression, not further appliance modification. This would involve optimizing the current biologic (adalimumab), increasing the dose of systemic corticosteroids, or adding another agent like cyclosporine. This distinction separates a dermatological/medical management problem from a purely stoma-nursing problem.