What is the diagnosis and treatment for red and brown macules on the palms and soles in a patient with psoriasis?

Diagnosis: Secondary Syphilis Until Proven Otherwise

In a patient with psoriasis who develops red and brown macules on palms and soles, the diagnosis is secondary syphilis until proven otherwise, and immediate VDRL/RPR testing is mandatory. 1, 2

Critical Diagnostic Distinction

The key to this diagnosis lies in recognizing features that are incompatible with psoriasis:

• Acute onset over weeks is inconsistent with psoriasis, which follows a chronic, stable course or gradual progression 1
• Red-brown macules are the hallmark of secondary syphilis, not psoriasis 1
• Palmoplantar psoriasis presents with hyperkeratotic, fissured plaques, not macules 1, 3
• Symmetric palmar and plantar involvement with copper-colored macules strongly favors syphilis 1

Immediate Diagnostic Workup

Before considering any treatment, you must rule out life-threatening infectious causes:

• Obtain VDRL/RPR testing immediately to rule out secondary syphilis, which classically presents with scaly palmoplantar lesions 2
• Assess for systemic symptoms (fever, lymphadenopathy, malaise) that may accompany secondary syphilis 1
• Obtain detailed sexual history and recent exposures 1
• Consider tick exposure history to rule out Rocky Mountain Spotted Fever, which has 5-10% mortality if untreated 2

Treatment Algorithm Once Syphilis is Confirmed

If serologic testing confirms secondary syphilis:

• Partner notification and treatment is mandatory 1
• Treatment follows CDC guidelines for secondary syphilis (typically benzathine penicillin G 2.4 million units IM single dose for immunocompetent patients)
• Never initiate psoriasis treatment without excluding syphilis first 2

If Syphilis is Excluded: Palmoplantar Psoriasis Management

Only after infectious causes are definitively ruled out, consider palmoplantar psoriasis treatment:

First-Line Topical Therapy

• High-potency topical corticosteroids (clobetasol propionate) under occlusion for palms and soles 4, 2, 5
• Combination with calcipotriene ointment or tazarotene gel 5
• Trial for 4-8 weeks before escalating 5

Second-Line: Systemic Therapy

• Acitretin 25 mg daily is first-line systemic treatment, with substantial improvement typically within 2 months 2, 6, 5
• Palmoplantar involvement justifies systemic therapy regardless of body surface area, as quality of life impact is disproportionate to BSA 4, 2

Third-Line: Phototherapy

• Soak PUVA (15-30 minute soak in methoxsalen solution) is highly effective for palmoplantar disease 4, 2, 5
• Targeted phototherapy with 308-nm excimer laser 4, 5
• Acitretin plus PUVA combination is particularly effective 6, 5

Fourth-Line: Alternative Systemic Agents

• Methotrexate or cyclosporine if acitretin fails or is contraindicated 4, 2, 5
• Avoid methotrexate due to hepatotoxicity and bone marrow toxicity when biologics are available 5
• Avoid cyclosporine due to nephrotoxicity when biologics are available 5

Fifth-Line: Biologic Therapy

• Adalimumab, infliximab, or ustekinumab for refractory cases 4, 2, 7
• Anti-IL-17A and anti-IL-23 agents show particular promise for palmoplantar disease 6
• Etanercept 50 mg twice weekly for 12 weeks, then 50 mg weekly maintenance 4, 8

Critical Pitfalls to Avoid

• Never start psoriasis treatment without ruling out secondary syphilis - this is a medical-legal and patient safety imperative 1, 2
• Do not assume new palmoplantar lesions in a psoriasis patient are simply disease progression - the morphology (macules vs. plaques) and timeline (acute vs. chronic) matter 1
• Avoid systemic corticosteroids as monotherapy in any form of psoriasis - they can trigger flares and are contraindicated 2, 9
• Do not delay treatment if Rocky Mountain Spotted Fever is suspected - mortality is 5-10% and increases with delayed doxycycline 2