What is the diagnosis and treatment for pruritic vesicles on the bridge of the nose in a patient with potential exposure to allergens or irritants?

Pruritic Vesicles on Bridge of Nose

Most Likely Diagnosis

The most likely diagnosis is dermatitis herpetiformis (DH), particularly given the facial location with pruritic vesicles, though allergic contact dermatitis and vesicular pemphigoid must also be considered in the differential. 1

Diagnostic Approach

Key Clinical Features to Assess

• Distribution pattern: DH classically presents on extensor surfaces (elbows, knees, buttocks), but facial involvement, while rare, is well-documented and can be the presenting feature 1
• Vesicle characteristics: Small, grouped, tense vesicles that are intensely pruritic 1, 2
• Symmetry: DH typically shows symmetric distribution, though this may not be apparent early in disease 3
• Associated symptoms: Ask about gastrointestinal symptoms suggesting celiac disease, as DH is a cutaneous manifestation of celiac disease 1

Essential Diagnostic Testing

Perform direct immunofluorescence (DIF) from perilesional skin—this is the gold standard for diagnosis. 1

• DH shows: Granular IgA deposits in the papillary dermis 1, 4
• Histopathology: Neutrophils in dermal papillae, subepidermal vesicles, though leukocytoclastic vasculitis can be a prominent feature 4
• Serologic testing: Check serum IgA anti-tissue transglutaminase antibodies (elevated in DH) 4

Alternative Diagnoses to Consider

Allergic contact dermatitis should be considered if there is:

• Clear temporal relationship to allergen exposure (cosmetics, fragrances, metals touching the nasal bridge) 5
• Erythema and edema preceding vesicle formation 5
• Note: Vesicular contact dermatitis can progress to erythema multiforme-like eruptions in severe cases 5

Vesicular pemphigoid presents with:

• Multiple small tense vesicles that may mimic DH clinically 3
• DIF shows linear IgG and C3 at the basement membrane zone (not granular IgA) 3
• May require systemic corticosteroids and immunosuppressants for control 3

Treatment Algorithm

For Confirmed Dermatitis Herpetiformis

Initiate a strict gluten-free diet immediately—this is the definitive treatment and addresses the underlying pathophysiology. 1, 4

For acute symptom control while awaiting dietary response:

• Topical dapsone 5% gel: Apply to affected areas; this has demonstrated efficacy for facial DH 1
• Systemic dapsone: Consider if topical therapy insufficient or widespread disease (requires G6PD screening before initiation) 1
• Symptomatic relief: Topical hydrocortisone can be applied to affected areas 3-4 times daily for pruritus 6

For Suspected Allergic Contact Dermatitis

If contact allergen exposure is suspected:

• Immediate avoidance of suspected triggers (eyeglasses, cosmetics, fragrances, metals) 7
• Topical corticosteroids: Apply hydrocortisone to affected area 3-4 times daily 6
• Patch testing: Perform after acute phase resolves (3 months post-remission) to identify specific allergens 5

For Vesicular Pemphigoid

If DIF shows linear basement membrane zone immunoreactants:

• Systemic corticosteroids: Required for initial control 3
• Steroid-sparing agents: Methotrexate or other immunosuppressants may be needed for maintenance 3

Critical Pitfalls to Avoid

• Do not dismiss facial involvement as excluding DH—while uncommon, facial DH is well-documented and can be misdiagnosed as allergic contact dermatitis 1
• Do not rely on histopathology alone—DIF is essential, as leukocytoclastic vasculitis can be the predominant histologic finding in DH, mimicking systemic vasculitis 4
• Do not delay gluten-free diet if DH is confirmed—dietary modification is the only treatment addressing the underlying disease and can lead to complete remission 1, 4
• Do not perform extensive vasculitis workup if petechiae are present without first considering DH, as leukocytoclastic vasculitis may be a prominent feature 4

When to Refer

Refer to dermatology immediately if:

• Diagnosis is uncertain after initial evaluation 7
• DIF or specialized immunopathologic studies are needed 1
• Disease is refractory to initial topical therapy 1
• Systemic immunosuppression is being considered 3