What is the appropriate evaluation and management for an adult male presenting with diarrhea and a penile rash?

Evaluation and Management of Diarrhea with Penile Rash

This presentation requires immediate consideration of reactive arthritis (formerly Reiter's syndrome) as part of a sexually transmitted infection syndrome, and the patient should be empirically treated for both gonorrhea and chlamydia while undergoing targeted diagnostic evaluation.

Initial Diagnostic Approach

The combination of diarrhea and penile rash suggests either:

1. Reactive arthritis following urethritis (classic triad: urethritis, conjunctivitis, arthritis - though incomplete presentations are common)
2. Concurrent STI with separate infectious diarrhea
3. Systemic disease with multi-organ involvement

Critical History Elements

• Sexual history: Recent unprotected intercourse, new partners, symptoms of urethritis (discharge, dysuria)
• Diarrhea characteristics: Duration, bloody/mucoid stools, volume, recent travel, food exposures
• Penile rash details: Location (glans, shaft, prepuce), appearance (vesicular, macular, papular, erosive), associated discharge
• Systemic symptoms: Fever, joint pain, eye symptoms, oral lesions

Diagnostic Testing

For Urethritis/STI Evaluation

Test immediately for gonorrhea and chlamydia using NAATs from:

• First-void urine specimen
• Urethral swab if discharge present
• Also test for syphilis (serology) and HIV 1

For Diarrhea Evaluation

Stool testing is indicated when 2:

• Fever present
• Bloody or mucoid stools
• Severe or persistent symptoms (>7 days)
• Immunocompromised status
• Recent travel

Test for: Salmonella, Shigella, Campylobacter, Yersinia, STEC, and C. difficile if recent antibiotic use 2

For Penile Rash Characterization

The penile rash requires differentiation between 3, 4:

• Infectious causes: Candida, bacterial infection, HSV, syphilis
• Inflammatory dermatoses: Reactive arthritis (circinate balanitis), psoriasis, eczema
• STI-related lesions: Primary syphilis chancre, HSV vesicles

Empiric Treatment

Start immediately while awaiting test results:

Recommended Regimen

Ceftriaxone 250 mg IM single dose
PLUS
Azithromycin 1 g orally single dose 1, 5

This covers both gonorrhea and chlamydia, which are the most critical treatable causes of urethritis that can lead to reactive arthritis 6.

Rationale for Empiric Treatment

• Compliance with follow-up is often poor
• Early treatment prevents complications including reactive arthritis
• Azithromycin is superior to doxycycline for M. genitalium 1
• Single-dose regimens ensure treatment completion 1

Additional Management Based on Findings

If Reactive Arthritis Suspected

Look for:

• Circinate balanitis (painless erosions on glans)
• Keratoderma blennorrhagicum (hyperkeratotic lesions on palms/soles)
• Conjunctivitis or uveitis
• Asymmetric oligoarthritis (especially lower extremity)

Treatment remains the same for the underlying STI; NSAIDs for symptomatic relief of arthritis.

If Candidal Balanoposthitis Present

Add topical antifungal (clotrimazole 1% cream twice daily for 7 days) if the penile rash shows:

• Erythematous patches with satellite lesions
• White plaques
• Associated pruritus 6

If Infectious Diarrhea Confirmed

Treat based on specific pathogen identified. Most bacterial diarrheas are self-limited and don't require antibiotics unless:

• Severe illness
• Immunocompromised
• Specific pathogens (Shigella, Campylobacter in certain cases) 2

Critical Pitfalls to Avoid

1. Don't delay STI treatment waiting for test results in symptomatic patients - reactive arthritis complications can be prevented with early treatment 1

2. Don't assume the penile rash is just "balanitis" without considering STI-related causes, especially syphilis which requires different treatment 3, 4

3. Don't forget partner notification - all sexual partners within 60 days must be evaluated and treated empirically 1

4. Don't overlook systemic disease - if the patient has joint pain, eye symptoms, or oral ulcers, reactive arthritis is likely and requires rheumatology follow-up

Follow-Up Instructions

• Abstain from sexual intercourse for 7 days after treatment and until partners are treated 1
• Return if symptoms persist after treatment completion
• Retest for gonorrhea and chlamydia in 3-6 months due to high reinfection rates 1
• If diarrhea persists >14 days, evaluate for parasitic infections 2

When to Refer

Immediate dermatology/urology referral if:

• Penile ulceration that doesn't respond to treatment
• Concern for premalignant lesions (indurated, non-healing)
• Severe inflammatory dermatosis requiring biopsy 3, 4

Rheumatology referral if:

• Reactive arthritis develops with persistent joint symptoms