Dermatology MCQ - Inflammatory Dermatoses - Wells syndrome

A 45-year-old woman presents with a recurrent, mildly painful, erythematous plaque on her forearm that resembles cellulitis but is not responsive to antibiotics. A biopsy is performed. The histopathology report describes 'flame figures' characterized by eosinophilic granules coating collagen bundles within a dense dermal infiltrate. What is the most likely diagnosis?

A. Bullous pemphigoid
B. Arthropod bite reaction
C. Wells syndrome
D. Eosinophilic fasciitis
E. Chronic urticaria

Correct Answer: C. Wells syndrome

Answer & Explanation

Explanation:

The presence of "flame figures" on histopathology is the pathognomonic finding for Wells syndrome (eosinophilic cellulitis).

• Key Diagnostic Clues:

  • Clinical: The presentation of a cellulitis-like plaque that is recurrent and unresponsive to antibiotics is classic. Lesions can also be urticarial or bullous.

  • Histopathologic: The hallmark is the flame figure, which is not a true vascular phenomenon but an alteration of collagen fibers caused by the deposition of major basic protein from degranulating eosinophils. This appears as eosinophilic material coating and obscuring collagen bundles in the dermis.

The other options, while they may involve eosinophils, are incorrect:

• A. Bullous pemphigoid: This is a subepidermal blistering disorder. Histopathology shows a subepidermal blister with numerous eosinophils. While eosinophils are prominent, flame figures are not a characteristic feature. The primary finding is linear deposition of IgG and C3 along the basement membrane zone on direct immunofluorescence.

• B. Arthropod bite reaction: This can have a very dense eosinophilic infiltrate and may occasionally show localized flame figures. However, Wells syndrome is a distinct clinical-pathological entity. The history of a recurrent, solitary plaque without a known bite, combined with the characteristic histology, points more strongly to Wells syndrome. The two can be difficult to distinguish.

• D. Eosinophilic fasciitis: This involves deep inflammation of the fascia, leading to peau d'orange skin induration and joint contractures. A deep biopsy to the fascia is required for diagnosis, showing inflammation and thickening of the fascia with eosinophils and lymphocytes. Flame figures are not a feature.

• E. Chronic urticaria: Histology typically shows a sparse perivascular infiltrate of lymphocytes and eosinophils with dermal edema. It does not feature the dense infiltrate or flame figures characteristic of Wells syndrome.

Key Associations for Wells Syndrome

• Pathophysiology: The cause is unknown. It is considered an inflammatory reactive process characterized by a massive infiltration and degranulation of eosinophils in the dermis. It can be associated with various triggers.

• Associated Conditions/Triggers:

  • Infections: (e.g., parasitic, viral).

  • Drugs.

  • Arthropod bites/envenomation.

  • Malignancy (rarely).

  • Often, it is idiopathic.

• Clinical Presentation: The classic lesion evolves through stages: an acute cellulitis-like phase, a subacute granulomatous phase, and a resolution phase. It can present with single or multiple plaques, and vesicles or bullae can form on the surface.

• Differential Diagnosis: The main differential is bacterial cellulitis. Other conditions include urticaria, bullous pemphigoid, and other eosinophilic dermatoses.

• Prognosis: The condition is characterized by recurrent, self-limited episodes. It is generally benign but can be chronic and cause significant discomfort.

• Management:

  • First-line: Oral corticosteroids (e.g., prednisone 0.5-1 mg/kg/day) are highly effective, leading to rapid resolution.

  • Second-line / Steroid-sparing agents: For recurrent disease, agents like dapsone, minocycline, or antihistamines can be used.