Topic Overview

Acrodermatitis Continua of Hallopeau (ACH)

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Definition and Overview

 

 

 

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• A rare, chronic, and sterile pustular skin disorder affecting the fingers or toes.

• Often involves the nail beds, leading to deformity or destruction of the distal phalanx.

• Considered a localized variant of pustular psoriasis with unique features and progression.

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Epidemiology

• Rarity: Uncommon disorder, mostly sporadic cases.

• Age of Onset: Can occur at any age, more common in adults and elderly.

• Gender Predominance: Slight female predominance.

Triggering Factors:

• Minor trauma, infections, external irritants.

• May be exacerbated by systemic corticosteroids.

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Clinical Features

Initial Presentation

• Primary Lesion:

  • Erythematous, scaly patches or plaques.

  • Sterile pustules at tips of fingers (rarely toes).

  • Commonly involves one or two digits, especially the thumb.

• Symptoms:

  • Pustules rupture → crusts or erosions.

  • Pain, tenderness, discomfort.

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Progression

 

 

 

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• Nail Involvement:

  • Nail folds, bed, matrix involvement →

    • Nail dystrophy

    • Complete loss of nail plates (onycholysis)

  • Chronic disease → permanent nail destruction

• Bone and Joint Changes:

  • Osteolysis (loss of distal phalanx)

  • Joint stiffness or deformity (resembles psoriatic arthritis)

• Spread:

  • Proximal extension along digit

  • May involve multiple digits

• Generalization:

  • Can progress to generalized pustular psoriasis (life-threatening)

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Morphological Patterns

• Localized Pattern: Limited to one/few digits, chronic course.

• Diffuse Pattern: Progressive spread with generalized pustulation.

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Pathogenesis

 

 

 

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• Autoimmune Nature:

  • Dysregulation of innate immunity

  • Neutrophil activation

  • Elevated IL-36 cytokines

• Genetic Associations:

  • Mutations in IL36RN

  • Mutations in AP1S3

• Triggers:

  • Trauma, stress, infections, irritants

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Histopathology

 

 

 

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• Subcorneal neutrophilic pustules (hallmark).

• Spongiform pustules, parakeratosis, epidermal thinning.

• Chronic cases:

  • Epidermal atrophy

  • Fibrosis

  • Dermal inflammation

• Key feature: Absence of infectious agents in pustules.

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Investigations

• Clinical diagnosis based on characteristic lesions.

• Laboratory tests:

  • Rule out bacterial/fungal infections (sterile pustules).

  • Genetic testing (IL36RN, AP1S3).

• Imaging:

  • X-ray → detect osteolysis or deformities.

• Histology:

  • Confirms neutrophilic pustules.

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Differential Diagnosis

• Infectious:

  • Herpetic whitlow

  • Candidiasis

• Inflammatory:

  • Psoriatic arthritis

  • Onychomycosis

  • Parakeratosis pustulosa

• Traumatic:

  • Traumatic onycholysis

  • Contact dermatitis

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Disease Course

• Chronic and relapsing.

• Persists for months to years.

Complications:

• Nail destruction

• Severe deformity and disability

• Spontaneous remission: Rare

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Management and Treatment

Local Treatments

 

 

 

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• Topical corticosteroids (with occlusion).

• Vitamin D analogues (calcipotriol).

• Topical tacrolimus.

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Systemic Treatments

 

 

 

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• First-line:

  • Acitretin (0.3–0.5 mg/kg/day)

  • Methotrexate

  • Ciclosporin

• Second-line:

  • Biologics:

    • TNF-α inhibitors (Infliximab, Adalimumab)

    • IL-17 inhibitors (Secukinumab)

    • IL-23 inhibitors (Ustekinumab)

  • IL-1 blockade: Anakinra

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Combination Therapy

• Acitretin + PUVA

• Methotrexate + biologics

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Supportive Care

• Protect digits from trauma.

• Treat secondary infections if present.

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Prognosis

• Localized ACH:

  • Treatable but relapsing

  • Functional impairment possible

• Generalized ACH:

  • Requires aggressive therapy

  • High morbidity

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Key Points

 

 

 

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• Early diagnosis prevents nail loss and bone deformities.

• IL36RN mutation testing helps guide biologic therapy.

• Long-term remission often requires multimodal treatmen