What are the common infections of the penile skin and their first-line treatments?

Common Penile Skin Infections and First-Line Treatments

The most common infections affecting penile skin are sexually transmitted infections (STIs), fungal infections (particularly Candida balanitis), and less commonly bacterial cellulitis, with treatment directed by the specific pathogen identified.

Sexually Transmitted Infections

Genital Herpes

Herpes simplex virus is the most common infectious cause of genital ulceration 1. Many infections are asymptomatic, making diagnosis challenging. The infection presents with painful vesicles that progress to ulcers on the penile shaft or glans.

Human Papillomavirus (HPV) / Genital Warts

Visible genital warts are most commonly caused by HPV types 6 or 11 2. The 2024 EAU guidelines provide the most current management approach 3. Treatment options include:

• Topical therapies: Imiquimod (immunotherapeutic agent that induces interferon) shows promise as first-line therapy 1
• Physical destruction: Cryotherapy, electrocautery, or surgical excision
• Important caveat: Recurrences are common regardless of treatment method 1

High-risk HPV types (16,18) are associated with premalignant lesions and require biopsy for diagnosis 2.

Gonococcal and Chlamydial Urethritis

When urethritis extends to involve penile skin or presents with discharge:

For gonococcal infection, the 2024 EAU guidelines recommend 3:

• Ceftriaxone 1 g IM or IV single dose PLUS Azithromycin 1 g PO single dose

For non-gonococcal urethritis (Chlamydia trachomatis) 3:

• Azithromycin 1.0-1.5 g PO single dose, OR
• Doxycycline 100 mg PO twice daily for 7 days

The dual therapy approach addresses both pathogens and emerging resistance patterns 3.

Syphilis

Primary syphilis presents as a painless chancre on the penis. All patients with genital lesions should receive syphilis serology 2.

Fungal Infections

Candida Balanitis

Candida albicans balanitis is the most frequent mycotic infection of the penis 4. The incidence is increasing and is primarily sexually transmitted 4. Risk factors include:

• Uncircumcised males (68% lower prevalence in circumcised males) 5
• Diabetes mellitus
• Immunocompromised states
• Poor hygiene

Clinical presentation: Erythema, pruritus, white discharge, and satellite lesions on the glans and prepuce.

First-line treatment 4, 6:

• Topical antifungal creams (clotrimazole, miconazole) applied twice daily for 7-14 days
• Address hygiene and consider sexual transmission
• Definitive treatment for recurrent cases: circumcision 5

Dermatophytic Infections (Tinea)

While tinea cruris (groin) is common, penile involvement is rare 1, 4. Treatment involves topical antifungals, with systemic therapy for widespread infection 4.

Bacterial Infections

Bacterial Cellulitis

Penile cellulitis presents with diffuse swelling, erythema, warmth, and tenderness of the penile shaft 7. Common in uncircumcised, sexually active adults, though can occur in circumcised males 7.

Causative organisms: Streptococcus species most common 7, though unusual organisms like Bacillus cereus have been reported 8.

Treatment approach:

• Broad-spectrum antibiotics covering Streptococcus and Staphylococcus
• Culture penile discharge or aspirate to guide therapy
• Ultrasound can support diagnosis and rule out abscess 7

Fournier's Gangrene (Life-Threatening Emergency)

This is an aggressive, frequently fatal polymicrobial soft-tissue infection requiring immediate recognition 3.

Clinical features 3:

• Painful swelling of scrotum/perineum with sepsis
• May have insidious onset (40% of cases)
• Risk factors: diabetes, immunocompromised, obesity, recent urogenital surgery

Critical management 3:

• Immediate broad-spectrum antibiotics on presentation
• Urgent repeated surgical debridement with urinary diversion via suprapubic catheter
• CT or MRI to define extent
• Common pitfall: Internal necrosis vastly exceeds external signs—high index of suspicion required, especially in obese patients

Parasitic Infections

Pediculosis Pubis (Pubic Lice)

Transmitted by sexual contact, presents with pruritus and visible lice/nits 9.

First-line treatment 9:

• Permethrin 1% cream rinse applied to affected areas, washed off after 10 minutes, OR
• Pyrethrins with piperonyl butoxide applied and washed off after 10 minutes

Alternative for resistance 9:

• Malathion 0.5% lotion applied for 8-12 hours, OR
• Ivermectin 250 μg/kg PO, repeated in 2 weeks (take with food)

Decontaminate bedding and clothing 9.

Scabies

Penis and scrotum are favorite locations for scabious lesions 1. Oral ivermectin is emerging as treatment of choice, though topical permethrin remains standard 1.

Diagnostic Approach

Essential workup for penile skin infections:

1. Sexual history: Recent partners, condom use, STI exposure
2. Examination: Note distribution (glans vs. shaft), presence of discharge, ulceration, or systemic signs
3. Laboratory testing:
   • NAAT for gonorrhea and chlamydia 10, 3
   • Syphilis serology and HIV testing 2
   • KOH preparation and fungal culture for suspected mycotic infection 4, 6
   • Bacterial culture for cellulitis or atypical presentations
4. Biopsy: Required when malignancy cannot be excluded clinically (e.g., persistent plaques, atypical lesions) 1

Key Clinical Pitfalls

• Don't miss Fournier's gangrene: Any penile/scrotal swelling with systemic signs requires urgent imaging and surgical consultation 3
• Treat sexual partners: For all STIs, partners within 60 days of symptom onset require evaluation and treatment 2, 3
• Consider HIV status: Immunocompromised patients have atypical presentations and broader differential (fungi, mycobacteria) 2
• Biopsy persistent lesions: Squamous cell carcinoma in situ can appear benign, leading to delayed diagnosis 1
• Address underlying conditions: Diabetes and immunosuppression predispose to fungal infections and Fournier's gangrene 3, 5