What is Erosive Pustular Dermatosis of the scalp?

Erosive Pustular Dermatosis of the Scalp

Erosive pustular dermatosis of the scalp (EPDS) is a rare chronic inflammatory condition characterized by sterile pustules, erosions, and crusting on the scalp that leads to scarring alopecia and skin atrophy, typically affecting elderly individuals with sun-damaged skin following local trauma or iatrogenic injury. 1, 2

Clinical Presentation

EPDS manifests with distinctive features that help differentiate it from other scalp conditions:

• Primary lesions: Extensive pustular lesions, erosions, and crusts located on the scalp 2
• Associated findings: Erythema, follicular pustules, and in advanced stages, irreversible scarring alopecia 2
• Skin characteristics: The surrounding skin typically shows chronic actinic (sun) damage 2, 3
• Sterile nature: The pustules and lakes of pus are sterile, distinguishing this from infectious processes 3

Pathogenesis and Predisposing Factors

The exact pathogenesis remains incompletely understood, but several key associations have been identified:

Iatrogenic triggers are the most common precipitating factors:

• Surgical procedures on the scalp 1, 4
• Physical injuries and trauma 4, 2
• Topical treatments for actinic keratoses 4
• Procedural treatments for androgenetic alopecia 4
• Photodynamic therapy (paradoxically can both cause and treat EPDS) 2, 5

Associated conditions include:

• Autoimmune disorders: rheumatoid arthritis, autoimmune hepatitis, Hashimoto thyroiditis, and Takayasu aortitis 2
• Androgenetic alopecia 2
• Lichen planopilaris 5

Diagnostic Approach

EPDS is fundamentally a diagnosis of exclusion requiring specific clinical context 2:

Key diagnostic criteria to establish:

• Elderly age (though can occur at any age) 2, 3
• Sun-damaged skin 2
• History of preceding trauma or iatrogenic injury 1, 4
• Clinical manifestations of pustules, erosions, and crusting 2

Histopathology findings are non-specific but supportive 2:

• Epidermal atrophy
• Focal erosions
• Mixed inflammatory infiltrate (neutrophils, lymphocytes, plasma cells)

Important exclusions:

• Bacterial cultures, fungal stains, and viral stains are typically negative and help rule out infectious etiologies 2
• Must differentiate from non-melanoma skin cancer, bullous autoimmune diseases, and soft tissue infections 3

Treatment Algorithm

First-line therapy: High-potency topical corticosteroids have been the historical standard 4, 2

Alternative topical options with excellent efficacy:

• Topical tacrolimus: Commonly used with few recurrences and adverse effects 4
• Topical dapsone: Successful with good tolerability 4
• Calcipotriol: Effective alternative 4, 2
• Silicone gels: Documented success 4

Systemic therapies for severe or refractory cases:

• Systemic glucocorticoids: Effective for extensive disease, as demonstrated in cases with delayed wound healing 1
• Oral dapsone: Reserved for disseminated disease 4
• Acitretin and isotretinoin: Successful in select cases 4
• Zinc sulfate: Should be considered when serum zinc levels are low 4
• Cyclosporine: Effective but limited by adverse effects 4

Procedural options:

• Photodynamic therapy: Effective in some patients, though paradoxically can induce disease in others 2, 5
• Curettage followed by aminolevulinic acid photodynamic therapy: Successful in cases associated with lichen planopilaris 5

Rarely needed: Systemic antibiotics or surgical intervention 3

Critical Clinical Pitfalls

Early recognition is paramount: Delayed diagnosis leads to irreversible cicatricial alopecia 1, 2. When erosive disease and delayed wound healing occur after scalp trauma or procedures, EPDS must be considered immediately 1.

Avoid misdiagnosis: EPDS resembles other dermatologic conditions and may easily be misdiagnosed 4, 3. The combination of elderly age, sun-damaged skin, preceding trauma, and sterile pustules should trigger consideration of EPDS 2.

Treatment selection considerations: While topical corticosteroids are traditional first-line therapy, alternative treatments like tacrolimus and photodynamic therapy may avoid recurrence and skin atrophy, particularly important in the elderly population 4. Timely treatment with systemic anti-inflammatory agents prevents cicatricial alopecia and mitigates further scalp damage 1.

Underrecognition: EPDS may be more common than previously recognized due to diagnostic challenges from non-pathognomonic histologic findings and overlapping clinical features 1.