Dermatology MCQ - Inflammatory Dermatoses - Amicrobial pustulosis of the skin folds

A 25-year-old woman with a known diagnosis of systemic lupus erythematosus (SLE) presents with a recurrent, pruritic eruption characterized by sterile pustules and erythematous plaques localized predominantly to the major skin folds, including the axillae and groin. Bacterial and fungal cultures of the pustules are negative. The most likely diagnosis is:

A. Hidradenitis suppurativa
B. Candidal intertrigo
C. Hailey-Hailey disease
D. Amicrobial pustulosis of the skin folds
E. Inverse psoriasis

Correct Answer: D. Amicrobial pustulosis of the skin folds

Answer & Explanation

Explanation:

The presentation of sterile pustules in the major skin folds (axillae, groin, inframammary) in a patient with a known autoimmune disease, particularly SLE, is highly characteristic of Amicrobial Pustulosis of the Skin Folds.

• Key Diagnostic Clues:

  • Distribution: Predilection for intertriginous areas.

  • Lesions: Sterile pustules on an erythematous base, which can coalesce into plaques.

  • Negative Cultures: The "amicrobial" nature is confirmed by negative bacterial and fungal cultures.

  • Strong Association with Autoimmunity: This condition is overwhelmingly associated with autoimmune diseases, most commonly SLE, but also other conditions like Sjögren's syndrome, rheumatoid arthritis, and inflammatory bowel disease.

The other options are incorrect:

• A. Hidradenitis suppurativa: This presents with deep, painful nodules, abscesses, and sinus tracts in the intertriginous areas. It is not characterized by superficial sterile pustules and is not specifically linked to SLE.

• B. Candidal intertrigo: This is a fungal infection that presents with beefy red erythema, satellite papules, and pustules in the folds. However, a potassium hydroxide (KOH) preparation or fungal culture would be positive, and it is not specifically associated with SLE.

• C. Hailey-Hailey disease: This is a genetic disorder (acantholysis) that presents with recurrent vesicles and erosions in the intertriginous areas, often with a macerated appearance. It is not characterized by sterile pustules and is not associated with autoimmune disease.

• E. Inverse psoriasis: This presents with well-demarcated, shiny, erythematous plaques in the skin folds, but it is typically non-pustular. Pustules in the folds would point more towards pustular psoriasis, which is a more generalized and severe condition, not typically confined to the folds.

Key Associations for Amicrobial Pustulosis of the Skin Folds

• Pathophysiology: Considered a neutrophilic dermatosis and an autoinflammatory condition. It is thought to be a cutaneous manifestation of the underlying autoimmune dysregulation.

• Associated Conditions: The association with autoimmune disease is paramount. Screening for an underlying autoimmune condition, especially if not previously diagnosed, is a critical part of the workup.

• Clinical Presentation: The eruption is often chronic and relapsing. It can be intensely pruritic or painful. The pustules are sterile and often appear on a background of erythema.

• Histopathology: Shows a neutrophilic dermatosis with subcorneal and/or intraepidermal spongiform pustules, similar to those seen in psoriasis. There is a dense dermal neutrophilic infiltrate.

• Differential Diagnosis: The main differentials are other intertriginous pustular conditions, as listed above. The key is the sterile nature and the association with autoimmunity.

• Prognosis: The course tends to parallel the activity of the underlying autoimmune disease. It can be chronic and difficult to treat.

• Management:

  1. Topical Therapies: High-potency topical corticosteroids are the first-line treatment.

  2. Systemic Therapies: For refractory or widespread disease, dapsone is often the most effective systemic agent due to its anti-neutrophilic properties. Other options include colchicine, oral corticosteroids, and hydroxychloroquine.

  3. Biologics: In cases resistant to the above, biologic agents used for the underlying autoimmune disease (e.g., rituximab for SLE) may also control the skin lesions.