What is dyshidrotic eczema (pompholyx) of the toes, and how is it diagnosed and managed?

Dyshidrotic Eczema of the Toes

Dyshidrotic eczema (pompholyx) affecting the toes is a recurrent vesicular eruption characterized by intensely pruritic, tense vesicles embedded deep in the epidermis that appear suddenly, typically on the lateral and ventral surfaces of the toes and soles. 1, 2

Clinical Presentation

The hallmark feature is the appearance of small, tense vesicles that resemble "tapioca pudding" on physical examination, which distinguishes this condition from other vesicular disorders. 2 The vesicles are:

• Strongly distended and painful when they enlarge due to the thick stratum corneum of plantar skin 3
• Embedded deep within the epidermis below the thick horny layer, making them appear as deep-seated blisters 1, 3
• Preceded by a period of ferocious pruritus that announces the eruption 3
• Self-limited, drying up and disappearing within three weeks, though relapses are frequent 3

The condition affects men and women equally and is more common in young adults, though it can occur at any age. 2

Diagnosis

Diagnosis is primarily clinical based on the characteristic vesicular morphology and distribution. 2 Key diagnostic features include:

• Histologic examination reveals spongiotic dermatitis with eczematous reaction around sweat ducts, though the sweat ducts themselves show no structural abnormalities 1, 4
• Immunofluorescence studies may demonstrate deposits of CD45, CD3, CD8, myeloperoxidase, IgE, C3, and fibrinogen within the epidermal spongiotic process, indicating a complex immunological response 4
• Rule out infectious causes (bacterial, fungal, viral), bullous pemphigoid, and scabies through appropriate testing 2

Metal allergy is regarded as one of the important potential etiologic factors, particularly in recurrent cases, and patch testing should be considered. 1

Management Algorithm

First-Line Topical Therapy

Start with moderate-to-high potency topical corticosteroids (prednicarbate 0.02% or betamethasone valerate 0.1%) applied twice daily for 2 weeks, which are the cornerstone of topical therapy. 5, 6

• Apply urea 10% cream at least daily to maintain skin hydration and address any hyperkeratotic changes 5
• Calcineurin inhibitors are effective alternatives when corticosteroid side effects are a concern 6

Second-Line Phototherapy

If no response after 4 weeks of topical therapy, refer for topical PUVA (psoralen plus UVA) therapy 2-3 sessions weekly, which achieves clearance or considerable improvement in 58-81% of dyshidrotic eczema cases. 7, 8 However:

• Oral PUVA demonstrates superior efficacy to topical PUVA, showing significant improvement or clearance in 81-86% of hand and foot eczema cases, though relapse rates are high 8
• Topical PUVA has not been demonstrated more effective than placebo in controlled trials, despite positive results in uncontrolled studies 8
• High-dose UVA-1 irradiation is as effective as systemic photochemotherapy 6

Systemic Therapy for Severe Disease

For recalcitrant bullous pompholyx, systemic corticosteroids combined with immunosuppressants are often necessary. 6 Specific options include:

• Alitretinoin has demonstrated efficacy in chronic hand dermatitis including pompholyx 6
• Mycophenolate mofetil has shown successful clearing in cases with complex immunological involvement 4
• Intradermal botulinum toxin injection is an evolving treatment option for selected cases 6

Adjunctive Measures

• Avoid mechanical stress, chemical irritants, and excessive moisture between toes 9
• Use pressure redistribution and cushioning, with appropriate footwear modifications 9
• Apply moisturizer after every foot wash using lukewarm water 5
• If metal allergy is identified through patch testing, remove the metal allergen, as this can lead to symptom improvement 1

Critical Pitfalls to Avoid

• Never perform aggressive blade debridement on vesicular lesions, as this can cause severe complications and increased blistering in fragile skin 7, 9
• Avoid prolonged high-potency corticosteroid use on thin skin areas to prevent atrophy 9
• Do not use chemical plasters for any hyperkeratotic changes, especially in diabetic patients 9
• Recognize that patients with atopy, sweat gland disorders, or neurovegetative disturbances have frequent relapses and require long-term management strategies 3

Expected Course

Most patients benefit from a combination of treatments rather than monotherapy. 6 The condition follows a relapsing course, with vesicles typically resolving within three weeks but recurring unpredictably. 3 Several clinical variants may develop, including bullous dyshidrosis, superinfection, and psoriasiform keratoderma, each requiring modification of the treatment approach. 3