What is the diagnosis and treatment for an adult patient with no significant past medical history presenting with dark dry patches on the palms of hands and feet?

Dark Dry Patches on Palms and Feet

The most likely diagnosis is palmoplantar psoriasis or hyperkeratotic hand-foot eczema, and first-line treatment should be clobetasol propionate 0.05% cream twice daily plus urea 10% cream three times daily to all affected areas. 1

Critical Life-Threatening Exclusions First

Before proceeding with routine dermatologic management, you must exclude conditions that can be fatal if missed:

• Rule out Rocky Mountain spotted fever immediately if the patient has any fever, headache, malaise, or recent tick exposure (within 2 weeks), as this presents with maculopapular rash involving palms and soles 2-4 days after fever onset and carries 5-10% mortality if untreated. 1, 2, 3 Start doxycycline empirically without waiting for confirmation if any systemic symptoms are present. 1, 3

• Check pregnancy status in women of childbearing age and measure serum bile acids if pregnant, as intrahepatic cholestasis of pregnancy predominantly affects palms and soles with pruritus (worse at night) and confers risk of stillbirth. 1, 3

Most Likely Diagnoses for Dark Dry Patches

The differential for palmoplantar hyperkeratosis with dark, dry patches includes:

• Palmoplantar psoriasis presents with well-demarcated erythematous plaques with thick silvery scale and hyperkeratosis, affecting 40% of hand-foot dermatosis cases. 1 In darker skin types, the "erythema" may appear as darker brown or hyperpigmented patches rather than red.

• Hyperkeratotic hand-foot eczema presents with vesicles, scaling, erythema, and fissuring with yellow-white scaling, affecting 31% of cases. 1 The "dry patches" may represent chronic lichenified eczema with post-inflammatory hyperpigmentation.

Essential History Elements

Obtain these specific details to narrow the diagnosis:

• Occupational exposures to irritants, allergens, chemicals, or wet work, as frequent hand washing or chemical exposure can exacerbate symptoms. 1
• Recent tick exposure or travel history to exclude RMSF. 1, 2
• Medication history including chemotherapy agents, as hand-foot syndrome from drugs like capecitabine, sorafenib, or 5-fluorouracil causes marked discomfort, swelling, and hyperkeratosis on palms and soles. 4, 2

First-Line Treatment Algorithm

Step 1: Initiate topical therapy immediately

• Apply clobetasol propionate 0.05% cream or ointment twice daily to all affected areas for both palmoplantar psoriasis and hyperkeratotic eczema. 1
• Add urea 10% cream three times daily to all affected areas, including after hand washing, for humectant and keratolytic effects. 1
• Use the "soak and smear" technique: soak hands/feet in plain water for 20 minutes, then apply moisturizer to damp skin to enhance penetration. 1

Step 2: Reassess after 4 weeks

• 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 and 50-67% of hyperkeratotic eczema. 1 Note that oral PUVA showed superior efficacy to UVB in controlled studies of hand eczema, though relapse rates were high. 4

Step 3: Consider systemic therapy for severe/refractory cases

• Initiate acitretin 25 mg daily for severe palmoplantar psoriasis, which demonstrates significant improvement in scaling, thickness, and erythema within 2 months. 1 Monitor lipid panels as elevations in triglycerides and cholesterol are common but manageable with fibrates or statins. 1

Critical Pitfalls to Avoid

• Never dismiss palmar lesions with fever as simple dermatitis—RMSF mortality increases dramatically with delayed doxycycline treatment. 1, 2, 3

• Do not confuse excoriations from scratching with primary rash—conditions like cholestasis in pregnancy have no primary rash, only secondary excoriations from intense pruritus. 1

• Avoid using only emollients without corticosteroids for inflammatory palmoplantar dermatoses—the evidence shows that moderate-to-high potency topical corticosteroids are necessary for effective treatment. 1, 2

• Do not delay phototherapy referral if topical therapy fails after 4 weeks, as prolonged ineffective treatment reduces quality of life without benefit. 1