Dermatology MCQ - Inflammatory Dermatoses - Bowel-associated dermatitis–arthritis syndrome

A 45-year-old woman, who underwent a Roux-en-Y gastric bypass for morbid obesity two years ago, presents with recurrent episodes of a flu-like illness accompanied by tender, non-pruritic pustules and erythematous macules on her trunk and proximal extremities. She also describes accompanying arthralgias and tenosynovitis. The most likely diagnosis is:

A. Pustular psoriasis
B. Acute generalized exanthematous pustulosis (AGEP)
C. Bowel-associated dermatitis–arthritis syndrome
D. Behçet's disease
E. Disseminated gonococcal infection

Correct Answer: C. Bowel-associated dermatitis–arthritis syndrome

Answer & Explanation

Explanation:

This clinical scenario is classic for Bowel-associated Dermatitis–Arthritis Syndrome (BADAS). The key features are:

• Predisposing Condition: The patient has a history of gastric bypass surgery, which is a classic surgical procedure associated with BADAS. It can also occur in patients with other bowel disorders like inflammatory bowel disease (IBD) or jejunoileal bypass (now historical).

• Systemic Symptoms: Recurrent flu-like symptoms (fever, malaise).

• Cutaneous Findings: A polymorphous eruption including pustules, vesicopustules, and erythematous macules.

• Musculoskeletal Findings: Non-destructive arthralgias/arthritis and tenosynovitis.

The other options are incorrect:

• A. Pustular psoriasis: This presents with sterile pustules, but it is typically not associated with a specific bowel surgery. The plaques are more confluent and psoriasiform, and it lacks the strong, recurrent flu-like prodrome and tenosynovitis.

• B. Acute generalized exanthematous pustulosis (AGEP): This is a severe drug reaction characterized by the acute, widespread onset of many sterile pustules on a background of edematous erythema. It is caused by a medication, not associated with bowel surgery, and is usually a single episode, not a recurrent condition.

• D. Behçet's disease: This shares features like pustules and arthritis. However, Behçet's is defined by recurrent oral and genital aphthosis, which is not mentioned here. It is also not specifically linked to gastric bypass surgery.

• E. Disseminated gonococcal infection (DGI): This can present with pustules, tenosynovitis, and fever. However, the pustules of DGI are typically few in number, acral, and hemorrhagic. It is an acute infection, not a recurrent syndrome, and would be associated with a positive culture, not bowel surgery.

Key Associations for Bowel-associated Dermatitis–Arthritis Syndrome

• Pathophysiology: The leading theory is bacterial overgrowth in surgically created blind loops or pouches of the small intestine. This leads to the formation of circulating immune complexes containing bacterial antigens, which subsequently deposit in the skin and synovium, triggering a neutrophilic inflammatory response.

• Associated Conditions:

  • Jejunoileal bypass (historically, for obesity).

  • Roux-en-Y gastric bypass.

  • Inflammatory Bowel Disease (IBD), particularly Crohn's disease.

  • Other causes of bowel stasis (e.g., diverticula, surgically created pouches).

• Clinical Presentation: The triad of skin lesions, arthralgias/arthritis, and flu-like symptoms is characteristic. The skin eruption is often migratory and can include a mix of macules, papules, pustules, and vesicopustules.

• Histopathology: Shows a neutrophilic dermatosis. Findings can range from a superficial perivascular neutrophilic infiltrate to subcorneal or intraepidermal pustules, resembling other neutrophilic conditions like Sweet syndrome.

• Differential Diagnosis: Includes other neutrophilic dermatoses (Sweet syndrome, PAPA syndrome), Behçet's disease, and rheumatoid arthritis with cutaneous manifestations.

• Prognosis: The course is typically chronic and recurrent, paralleling the underlying bowel pathology.

• Management:

  1. Antibiotics: The first-line treatment is systemic antibiotics to target bacterial overgrowth. Options include tetracyclines (e.g., doxycycline), metronidazole, or clindamycin.

  2. Nutritional Support: Correction of nutritional deficiencies is important.

  3. Immunosuppression: For refractory cases, systemic corticosteroids or other immunosuppressants (e.g., colchicine, dapsone, TNF-alpha inhibitors) may be necessary.

  4. Surgical Reversal: In severe, intractable cases, surgical revision or reversal of the bypass may be required.