What is the appropriate treatment for a large, circular, itchy, and well-circumscribed plaque accompanied by xerosis on the posterior heel?

Treatment of Large Circular Itchy Plaque with Xerosis on Posterior Heel

For a large, circular, itchy, well-circumscribed plaque with xerosis on the posterior heel, initiate treatment with a moderate-to-high potency topical corticosteroid (class 2-5) combined with urea 10% cream applied twice to three times daily, while addressing any underlying mechanical stress factors. 1, 2

Primary Treatment Approach

Topical Corticosteroid Therapy

• Apply a moderate-to-high potency topical corticosteroid (class 2-5) twice daily for up to 4 weeks maximum to the well-circumscribed plaque, as this presentation is consistent with localized psoriasis or eczematous dermatitis 1
• The posterior heel location tolerates higher potency steroids better than intertriginous or facial areas, allowing for more aggressive initial treatment 1
• Avoid ultra-high potency steroids (class 1) unless under dermatological supervision due to risk of skin atrophy, particularly important given the xerosis already present 1

Xerosis Management

• Apply urea 10% cream three times daily to address the xerosis component, which is FDA-approved for hyperkeratotic conditions including dry, rough skin, dermatitis, psoriasis, and xerosis 2
• Urea acts as both a humectant and keratolytic agent, promoting normal healing of hyperkeratotic surface lesions 2
• The combination of emollient therapy with corticosteroids enhances overall efficacy and prevents the dry, cracked skin that perpetuates the itch-scratch cycle 3, 4

Mechanical Stress Reduction

Critical Behavioral Modifications

• Avoid mechanical stress to the heel: no prolonged walking, ensure cushioned shoes with proper heel support, and avoid barefoot walking 5
• The posterior heel is particularly susceptible to friction and pressure, which can trigger Koebnerization (trauma-induced lesion formation) in psoriasis 5
• Avoid chemical stress from skin irritants, solvents, or disinfectants that could worsen the condition 5

Treatment Algorithm

Week 0-2: Initial Phase

• Moderate-to-high potency topical corticosteroid twice daily 1
• Urea 10% cream three times daily 2
• Implement mechanical stress avoidance strategies 5
• Reassess after 2 weeks for improvement 5

Week 2-4: Continuation or Escalation

• If improving: Continue current regimen until complete clearance, but do not exceed 4 weeks of continuous corticosteroid use 1
• If no improvement or worsening: Consider adding vitamin D analog (calcipotriene) to the corticosteroid for synergistic effect, or refer to dermatology 1
• The well-circumscribed, hypertrophic nature suggests possible treatment resistance requiring specialist evaluation 5

Week 4+: Maintenance Phase

• Transition to weekend-only corticosteroid application while continuing urea cream daily to prevent relapse 1
• Consider vitamin D analog (calcipotriene) on weekdays as steroid-sparing maintenance 1

Important Clinical Considerations

Differential Diagnosis Implications

• The circular, well-circumscribed plaque pattern on the posterior heel strongly suggests localized plaque psoriasis, though eczematous dermatitis or lichen simplex chronicus remain possibilities 5, 1
• Repetitive scratching from pruritus can create fixed, hypertrophic plaques through Koebnerization, making the lesion more treatment-resistant 5
• Xerosis is both a contributing factor and consequence of the inflammatory process, requiring simultaneous treatment 6, 4

Common Pitfalls to Avoid

• Do not prescribe refills without clinical reassessment, as prolonged corticosteroid use can cause skin atrophy, particularly concerning given pre-existing xerosis 1
• Do not exceed 100g of moderate potency corticosteroid per month 1
• Avoid systemic corticosteroids entirely, as they can precipitate severe psoriasis flares upon discontinuation 1, 7
• Patient-perceived "treatment failure" is often due to poor adherence rather than true resistance; ensure clear application instructions 5

When to Refer to Dermatology

• Lack of improvement after 6 weeks of appropriate topical therapy 5
• Lesion extends beyond localized area or new lesions develop elsewhere 1
• Severe hyperkeratosis requiring more aggressive keratolytic therapy 5
• Need for systemic therapy consideration if topical treatment fails 1

Adjunctive Pruritus Management

If Pruritus Persists Despite Treatment

• Consider adding topical doxepin for up to 8 days (limited to <10% body surface area) for severe itch 5
• Topical clobetasone butyrate (moderate-potency steroid) or menthol-containing preparations may provide additional antipruritic benefit 5
• Avoid topical antihistamines long-term due to limited efficacy and potential for contact sensitization 5