What are the differential diagnoses and appropriate management for a patient presenting with itchy, scaling palms and soles?

Itchy and Scaling Palms and Soles: Diagnosis and Management

Start with super-potent topical corticosteroids (clobetasol 0.05%) under occlusion for 8–12 weeks, but first rule out secondary syphilis with RPR/VDRL testing and exclude Rocky Mountain Spotted Fever if fever or systemic symptoms are present—both can be fatal if missed.

Critical First Steps: Rule Out Life-Threatening Conditions

Before treating as a benign dermatosis, you must exclude two potentially fatal diagnoses:

• Obtain RPR or VDRL plus treponemal testing immediately in any patient with symmetric palm-plantar pruritus to rule out secondary syphilis, which presents with red-brown macules and can cause significant morbidity if untreated 1, 2.

• If fever, headache, or recent tick exposure is present, start doxycycline empirically while checking complete blood count for thrombocytopenia—Rocky Mountain Spotted Fever carries 5–10% mortality and half of deaths occur within 9 days of symptom onset 1, 3.

• Check ferritin or complete blood count in patients with chronic generalized pruritus without primary skin lesions, as iron deficiency accounts for roughly one-quarter of such cases and improves rapidly with replacement 1.

Key Differential Diagnoses

Palmoplantar Psoriasis

• Well-demarcated, erythematous plaques with thick silvery scale and hyperkeratosis affecting palms and soles, often with fissuring and significant functional disability 4, 1, 3.
• Affects approximately 40% of psoriasis patients and causes disproportionate quality-of-life impairment despite small body surface area 4, 2.

Pompholyx (Dyshidrotic Eczema)

• Intensely pruritic vesicles on lateral fingers and palms that look like "tapioca pudding," lasting approximately three weeks per flare 1, 5, 6.
• Strongly associated with atopic diathesis, hyperhidrosis, and neurovegetative disturbances 5, 7.
• Antihistamines are ineffective because this is not IgE-mediated 1.

Hyperkeratotic Hand-Foot Eczema

• Yellow-white scaling with vesicles, erythema, and fissuring affecting 31% of hand eczema cases 3.

Treatment Algorithm

First-Line: Intensive Topical Therapy (8–12 Weeks)

• Apply clobetasol propionate 0.05% cream or ointment twice daily under occlusion (plastic wrap, gloves, or socks overnight) to affected areas 4, 1, 3.

• Combine with calcipotriene ointment or tazarotene gel for synergistic efficacy in psoriatic lesions 3, 2.

• Use urea 10% cream three times daily, including after hand washing, for keratolytic and humectant effects; increase to 40% for severe localized thickening 1, 3.

• Employ "soak-and-smear" technique: soak hands/feet in plain water for 20 minutes, then immediately apply thick moisturizer to damp skin to enhance penetration 1, 3.

• Physical debridement with emery board or nail file after soaking can be used for mild hyperkeratosis, but avoid overdebridement as it increases blistering and tenderness 3.

Second-Line: Phototherapy (If No Response After 4 Weeks)

• Soak PUVA (psoralen immersion followed by UVA) 2–3 times weekly for several months achieves clearance in 58–81% of dyshidrotic eczema and 50–67% of hyperkeratotic eczema 4, 3.

• The risk of cutaneous malignancy on palms/soles after topical PUVA is very rare, unlike oral PUVA 4.

• Narrowband UVB or 308-nm excimer laser can be used for localized lesions when PUVA is unsuitable 4, 2.

Third-Line: Systemic Therapy (Severe or Refractory Disease)

Obtain baseline CBC, liver function tests, and lipid panel before initiating systemic therapy 3, 2.

Acitretin (First-Line Systemic Agent)

• Start acitretin 25 mg orally daily for severe palmoplantar psoriasis or refractory pompholyx 4, 3, 2.
• Expect substantial improvement within approximately 2 months, with reduction in scaling, thickness, and erythema 4, 3.
• After achieving control, taper to 25 mg on alternate days while maintaining benefit 4, 3.
• Monitor lipids and liver enzymes every 1–2 months because acitretin raises triglycerides and cholesterol 4, 3.
• Manage hypertriglyceridemia with fibrates and hypercholesterolemia with statins, but never combine both agents concurrently due to rhabdomyolysis risk 4, 2.

Alternative Systemic Agents

• Methotrexate 15–25 mg weekly is effective but requires monitoring for hepatotoxicity and bone-marrow suppression 4, 2.
• Cyclosporine 2.5–5 mg/kg daily is effective but limit to ≤1 year due to nephrotoxicity; monitor renal function and blood pressure regularly 4, 2.

Fourth-Line: Biologic Therapy (Refractory Palmoplantar Psoriasis)

• IL-17, IL-12/23 (ustekinumab), or IL-23 inhibitors are preferred over TNF-α blockers because head-to-head trials demonstrate higher skin-clearance rates 1, 2.

• TNF-α inhibitors (adalimumab, infliximab) remain effective but may paradoxically induce pustular psoriasis of palms/soles in approximately 1–2% of treated patients, even in those without prior psoriasis history 4, 1, 2.

• Biologic therapy is justified when intensive topical therapy or photochemotherapy fails to achieve adequate improvement, given the disproportionate quality-of-life impact 4.

Critical Pitfalls to Avoid

• Never dismiss symmetric palmoplantar rash without syphilis serology—assuming simple dermatitis without testing can lead to significant individual and public-health morbidity 1, 2.

• Never delay doxycycline if RMSF is suspected—mortality increases dramatically with delayed treatment, and half of deaths occur within 9 days 1, 3.

• Never use systemic corticosteroids as monotherapy in psoriasis—they can precipitate severe flares, including life-threatening generalized pustular psoriasis 1, 2.

• Never assume antihistamines will help pompholyx—the condition is not IgE-mediated and cetirizine does not relieve pruritus 1.

• Never combine fibrates and statins concurrently when managing acitretin-induced hyperlipidemia due to rhabdomyolysis risk 4, 2.

When to Refer to Dermatology

• Failure of intensive topical therapy after 8–12 weeks of occlusive super-potent corticosteroids warrants dermatology referral 1, 3.

• Need for systemic or biologic agents—initiation of acitretin, methotrexate, cyclosporine, or biologics should be supervised by a dermatologist 4, 1.

• Consideration of phototherapy or intradermal botulinum toxin requires specialist evaluation 1, 8.