What is Bullous Wells syndrome, a condition characterized by erythematous and edematous plaques, in a patient with a history of atopic dermatitis and long-term use of topical corticosteroids (steroids)?

What is Bullous Wells Syndrome?

Bullous Wells syndrome (eosinophilic cellulitis) is a rare inflammatory dermatosis characterized by sudden-onset erythematous, edematous plaques that can evolve into bullae, with distinctive histopathologic "flame figures" representing eosinophilic infiltration and degranulation in the dermis. 1, 2

Clinical Presentation

The condition presents with specific clinical features that distinguish it from other bullous disorders:

• Acute phase: Sudden appearance of annular or circinate erythematous-edematous patches that are tender, pruritic, and may be urticarial 1, 2
• Evolution: Lesions rapidly progress to morphea-like blue-slate-colored plaques, and in bullous variants, vesicles and bullae develop 1, 3
• Distribution: Typically affects the limbs (arms and legs), though facial involvement can occur 1, 3, 4
• Systemic features: Patients may experience fever, malaise, arthralgia, and peripheral blood eosinophilia, though blood hypereosinophilia is not constant 1, 5

Diagnostic Criteria

Wells syndrome diagnosis requires three key elements:

• Clinical: Sudden onset of erythematous-edematous patches evolving to plaques or bullae 1
• Histopathologic: Presence of "flame figures" (eosinophilic infiltrates with collagen degeneration) in the dermis, with granulomatous eosinophilic infiltrates 1, 2, 4
• Laboratory: Non-constant peripheral blood eosinophilia 1, 2

Critical Diagnostic Pitfall

Do not confuse bullous Wells syndrome with bullous pemphigoid in elderly patients with atopic history. The key distinguishing feature is that Wells syndrome shows eosinophilic infiltrates with flame figures on histopathology, while bullous pemphigoid requires positive direct immunofluorescence (DIF) showing linear IgG/C3 deposits at the dermoepidermal junction 6, 7. In your patient with atopic dermatitis and long-term topical steroid use, bullous pemphigoid must be excluded with DIF testing 6.

Triggering Factors and Associations

Wells syndrome is often idiopathic but can be triggered by:

• Infections: Arthropod bites, viral, bacterial, or parasitic infections (including tinea pedis and onychomycosis) 2, 3
• Medications: Various drugs, though specific agents are not well-characterized 1, 2
• Malignancy: Association with chronic lymphocytic leukemia and other hematologic conditions has been reported 5
• Immunotherapy: Checkpoint inhibitors can cause similar eosinophilic dermatoses, though these are typically classified separately 8

Treatment Approach

For localized disease, topical corticosteroids are first-line therapy and can achieve rapid resolution within weeks. 1, 2, 4

Treatment Algorithm:

1. Localized lesions: High-potency topical corticosteroids as initial therapy 1, 4
2. Widespread or refractory disease: Consider systemic corticosteroids, though systemic treatment should be limited given the benign, self-resolving nature 2
3. Recurrent disease: Identify and treat underlying triggers (e.g., fungal infections with oral terbinafine if tinea is present) 3
4. Steroid-resistant cases: Alternative options include dapsone, cyclosporine, antihistamines, or doxycycline, though evidence is limited to case reports 2

Important Treatment Considerations:

• Natural history: The disease typically has a benign course with spontaneous remission within weeks, though recurrences are frequent and may persist for years 2
• Avoid overtreatment: Given the self-limiting nature, aggressive systemic therapy should be reserved for widespread or treatment-resistant cases 2
• Address triggers: Treating underlying conditions (fungal infections, discontinuing offending medications) may lead to complete remission 3

Prognosis

Wells syndrome generally has an excellent prognosis with spontaneous resolution, though recurrences are common over several years 2, 5. Complete remission can be achieved when underlying triggers are identified and treated 3.