Dermatology MCQ - Inflammatory Dermatoses - Aseptic abscess syndrome

A 30-year-old woman with a history of Crohn's disease presents with recurrent episodes of fever and severe abdominal pain. Imaging studies reveal deep, sterile collections in the spleen and mesentery that do not respond to broad-spectrum antibiotics. A diagnosis of aseptic abscess syndrome is considered. Which of the following is the most characteristic and defining feature of these abscesses?

A. They are consistently associated with a positive bacterial culture for Escherichia coli.
B. They demonstrate a rapid and complete response to treatment with intravenous antibiotics.
C. They are characterized by a neutrophilic infiltrate on histology but remain culture-negative.
D. They are exclusively located in the subcutaneous tissue without visceral involvement.
E. They are associated with a specific serum autoantibody, anti-saccharomyces cerevisiae (ASCA).

Correct Answer: C. They are characterized by a neutrophilic infiltrate on histology but remain culture-negative.

Answer & Explanation

Explanation:

The term "Aseptic Abscess Syndrome" is defined by its core characteristics:

• "Aseptic" / "Sterile": The abscesses do not yield any bacterial, fungal, or mycobacterial growth on culture despite a classic abscess presentation. This is the most critical defining feature and is why they fail to respond to antibiotics.

• "Abscess": Histopathologic examination shows a massive infiltrate of neutrophils forming a true abscess, identical to an infectious one.

• Syndrome: It is a systemic inflammatory disorder, often associated with underlying conditions like Inflammatory Bowel Disease (IBD), particularly Crohn's disease, as in this vignette.

The other options are incorrect:

• A. They are consistently associated with a positive bacterial culture: This is the opposite of the definition; they are, by nature, culture-negative.

• B. They demonstrate a rapid and complete response to treatment with intravenous antibiotics: Their lack of response to antibiotics is a key clinical clue that distinguishes them from pyogenic abscesses and prompts the search for an alternative diagnosis.

• D. They are exclusively located in the subcutaneous tissue without visceral involvement: While subcutaneous abscesses can occur, the syndrome is defined by deep visceral involvement. The spleen is the most commonly affected organ, followed by lymph nodes, liver, and mesentery.

• E. They are associated with a specific serum autoantibody, anti-saccharomyces cerevisiae (ASCA): While ASCA is a serologic marker associated with Crohn's disease (the underlying condition in this case), it is not a specific marker for the abscesses themselves. The diagnosis is based on the clinical, radiological, and microbiological findings, not a specific antibody.

Key Associations for Aseptic Abscess Syndrome

• Pathophysiology: It is classified as a neutrophilic dermatosis with systemic involvement, similar to Sweet syndrome or pyoderma gangrenosum. It is an autoinflammatory disorder driven by dysregulated innate immunity.

• Associated Conditions: The most powerful association is with Inflammatory Bowel Disease (IBD), especially Crohn's disease. Other associations include other autoimmune diseases like rheumatoid arthritis and relapsing polychondritis.

• Clinical Presentation: Patients present with constitutional symptoms (fever, weight loss) and pain related to the location of the abscess(es). The most common sites are the spleen, abdominal lymph nodes, and mesentery.

• Diagnosis: This is a diagnosis of exclusion. It requires:

  1. Radiologic evidence of an abscess (on CT or MRI).

  2. Negative cultures from aspirated or drained material (bacterial, fungal, mycobacterial).

  3. Lack of response to broad-spectrum antibiotics.

  4. Rapid response to systemic corticosteroids.

• Differential Diagnosis: The main differential is a pyogenic abscess. Other causes of sterile inflammation, such as lymphoma or metastatic cancer, must also be ruled out.

• Prognosis: The condition is often chronic and relapsing. The prognosis is tied to the severity of the underlying IBD and the response to immunosuppressive therapy.

• Management:

  • First-line: Systemic corticosteroids (e.g., prednisone 1 mg/kg/day) are the cornerstone of treatment and typically produce a dramatic response.

  • Steroid-Sparing Agents: For long-term management and to prevent recurrences, immunosuppressants like azathioprine, infliximab (anti-TNFα), or colchicine are used.