Differentiating and Treating Fungal Acne vs Acne Vulgaris
When patients present with monomorphic truncal papules and pustules that are uniform in appearance, consider microbiologic testing to diagnose pityrosporum folliculitis (fungal acne), which requires antifungal rather than standard acne therapy. 1
Clinical Differentiation
Acne Vulgaris Presentation
- Polymorphic lesions including open/closed comedones (blackheads/whiteheads), inflammatory papules, pustules, and nodules 1
- Primarily facial involvement with possible truncal extension 1
- Varied lesion sizes and stages of development present simultaneously 2
- Associated with follicular hyperkeratinization, Cutibacterium acnes colonization, sebum production, and inflammation 1
Pityrosporum Folliculitis (Fungal Acne) Presentation
- Monomorphic truncal papules and pustules that appear uniform in size and appearance 1
- Pruritic lesions (itching is more common than in acne vulgaris) 1
- Truncal distribution predominantly affecting chest, back, and shoulders 1
- Lack of comedones - no blackheads or whiteheads present 1
- Often occurs after prolonged antibiotic use or in settings of increased heat/humidity 1
Diagnostic Approach
When to Consider Microbiologic Testing
Microbiologic testing should be performed for patients presenting with monomorphic truncal papules and pustules to diagnose pityrosporum folliculitis. 1
- Routine microbiologic testing is not recommended for typical acne vulgaris 1
- Consider testing for Gram-negative folliculitis in patients with eruptive uniform pustules to nodules in periorificial areas, particularly after prolonged tetracycline treatment 1
- KOH preparation or fungal culture can confirm Malassezia species in suspected fungal acne 1
Treatment Algorithms
Acne Vulgaris Treatment (Based on Severity)
Mild Acne:
- Topical retinoids (adapalene, tretinoin, tazarotene, or trifarotene) as monotherapy or with benzoyl peroxide 1
- Benzoyl peroxide combinations with antibiotics (erythromycin or clindamycin) 1
Moderate to Severe Acne:
- Topical retinoid plus benzoyl peroxide plus systemic antibiotics (doxycycline, minocycline, or sarecycline) 1
- Limit systemic antibiotics to maximum 12 weeks and always combine with benzoyl peroxide to prevent resistance 2, 3
- Consider hormonal agents (combined oral contraceptives or spironolactone) for appropriate candidates 1
Severe/Recalcitrant Acne:
- Isotretinoin for patients with psychosocial burden, scarring, or treatment-resistant disease 1, 3
- Daily dosing preferred over intermittent dosing 1
Pityrosporum Folliculitis Treatment
First-line antifungal therapy is required - standard acne treatments will fail:
- Topical azole antifungals: ketoconazole 2% cream/shampoo or miconazole 4
- Oral antifungals for extensive or resistant cases: itraconazole or ketoconazole 4
- Fluconazole and voriconazole show no activity against the causative organisms 4
Critical Pitfalls to Avoid
Do not treat pityrosporum folliculitis with antibiotics - this will worsen the condition by further disrupting skin flora and promoting fungal overgrowth 1, 4
Do not use topical antibiotics as monotherapy for acne vulgaris due to resistance development 1
Do not continue systemic antibiotics beyond 12 weeks for acne vulgaris 2, 3
Always combine benzoyl peroxide with any antibiotic therapy (topical or systemic) to prevent bacterial resistance 1
Key Distinguishing Features Summary
The most reliable clinical clue is lesion morphology: monomorphic uniform papulopustules on the trunk suggest fungal etiology requiring microbiologic confirmation, while polymorphic lesions with comedones on the face indicate acne vulgaris requiring standard acne therapy 1. When in doubt with atypical truncal presentations, obtain microbiologic testing before initiating prolonged antibiotic therapy that could exacerbate undiagnosed fungal folliculitis 1.