Diagnosis: Secondary Syphilis Until Proven Otherwise
This presentation of red and brown macules on the palms and soles in a 40-year-old male requires immediate serologic testing for syphilis (RPR/VDRL and treponemal-specific testing) before considering this as palmoplantar psoriasis, as the acute onset and characteristic distribution pattern strongly favor secondary syphilis. 1, 2
Critical Diagnostic Distinctions
Why This is Likely NOT Psoriasis
- Morphology mismatch: Palmoplantar psoriasis presents with hyperkeratotic, fissured plaques—not red-brown macules 1, 3
- Temporal pattern: The acute onset of lesions over weeks is inconsistent with psoriasis, which follows a chronic, stable course or gradual progression 1
- Distribution pattern: The symmetric palmar and plantar involvement with copper-colored macules is pathognomonic for secondary syphilis 1, 2
Why This is Likely Secondary Syphilis
- Classic presentation: Symmetric palmoplantar involvement with red-brown (copper-colored) macules is the hallmark of secondary syphilis 1, 2
- History of psoriasis is a red herring: The patient's knee psoriasis does not explain this new acute presentation with different morphology 1
Immediate Diagnostic Workup
Mandatory Testing
- Serologic testing: Order both RPR/VDRL and treponemal-specific testing (FTA-ABS or TP-PA) to confirm syphilis diagnosis 1, 2
- HIV screening: Syphilis and HIV frequently coexist, making concurrent HIV testing mandatory 1
- Complete blood count: Rule out Rocky Mountain Spotted Fever (RMSF), which can present similarly but shows thrombocytopenia 2
- Tick exposure history: RMSF has 5-10% mortality if untreated and requires immediate doxycycline 2
Critical Pitfall to Avoid
Never start treatment without ruling out secondary syphilis—this is a potentially life-threatening infectious disease requiring partner notification and treatment. 1, 2
Treatment Algorithm
If Syphilis is Confirmed
- Primary treatment: Benzathine penicillin G 2.4 million units IM as a single dose (standard treatment for secondary syphilis based on CDC guidelines) 1
- Partner notification: Mandatory contact tracing and treatment of sexual partners 1
- Follow-up serology: Monitor RPR/VDRL titers at 3,6, and 12 months to confirm treatment response 1
If Syphilis is Ruled Out and Palmoplantar Psoriasis is Confirmed
Only proceed with psoriasis treatment after infectious causes are definitively excluded 2:
First-Line Therapy
- Topical regimen: Superpotent topical corticosteroids (clobetasol propionate) under occlusion combined with calcipotriene ointment or tazarotene gel 4, 5
- Trial duration: 4-8 weeks before escalating therapy 5
Second-Line Therapy (if inadequate response after 4-8 weeks)
- Systemic retinoids: Acitretin 25 mg daily, with substantial improvement typically within 2 months 2, 5
- Targeted phototherapy: 308-nm excimer laser or soak PUVA (15-30 minutes in methoxsalen solution) 4, 5
Third-Line Therapy (if second-line fails after 2 months)
- Methotrexate or cyclosporine: Both are effective, but consider hepatotoxicity/bone marrow toxicity (MTX) versus nephrotoxicity (cyclosporine) 4, 5
- Biologic agents: Adalimumab, infliximab, or ustekinumab for refractory cases 4, 2, 5
Rationale for Systemic Therapy in Palmoplantar Disease
Quality of life impact from palmoplantar psoriasis is disproportionate to body surface area involved, justifying systemic therapy even when only hands and feet are affected. 4, 2 The condition is frequently debilitating, painful, and interferes with basic functions like walking or buttoning clothing 4.
Additional Clinical Pearls
Paradoxical Psoriasis
- TNF-alpha antagonists can paradoxically induce pustular psoriasis of the palms and soles in patients without prior psoriasis history 4
- This patient's existing knee psoriasis makes this less likely, but worth noting if biologics are considered