What are the characteristics and treatment of fungal acne?

Recognizing Fungal Acne (Pityrosporum/Malassezia Folliculitis)

Fungal acne presents as monomorphic, pruritic papules and pustules—typically 1-2mm in size—concentrated on the forehead extending into the hairline, upper back, and chest, and it should be suspected when acne-like lesions fail to respond to or worsen with traditional acne antibiotics. 1, 2

Key Clinical Features That Distinguish Fungal Acne

Lesion Characteristics

• Uniform appearance: Lesions are remarkably monomorphic (all look the same size and shape), unlike typical acne vulgaris which shows pleomorphic lesions (comedones, papules, pustules, nodules of varying sizes) 1, 3
• Size: Characteristically small, 1-2mm papules and pustules 1
• Pruritus: Present in 65-72% of cases—this is a critical distinguishing feature, as bacterial acne is rarely itchy 1, 2

Distribution Pattern

• Forehead and hairline: Lesions extending into the hairline are highly characteristic 1
• Upper trunk: Chest (70% of cases) and back/shoulders (69% of cases) are the most common sites 2
• Face and posterior arms: Also frequently involved 3

High-Risk Clinical Scenarios

Recent Antibiotic Use

• Over 75% of patients with fungal acne had recently been treated with antibiotics for presumed bacterial acne 1
• Fungal acne commonly develops as a new acneiform eruption following antibiotic therapy because antibiotics alter the normal skin flora, allowing yeast overgrowth 2, 3

Treatment Failure Pattern

• 40.5% of patients report unsuccessful treatment with traditional acne medications 2
• Lesions that worsen or fail to improve with standard acne therapy (retinoids, benzoyl peroxide, oral antibiotics) should raise suspicion 4, 3

Concurrent Conditions

• Immunosuppression or conditions altering normal skin flora increase risk 3
• May coexist with bacterial acne vulgaris, requiring treatment of both conditions simultaneously 4

Diagnostic Confirmation

Potassium Hydroxide (KOH) Preparation

• This is the definitive diagnostic test: KOH prep from pustule exudate reveals fungal spores and hyphae consistent with Malassezia yeast 1, 4
• The test distinguishes fungal folliculitis from bacterial acne by demonstrating yeast in the follicular lumen 2
• Should be performed when clinical suspicion exists, particularly in treatment-resistant cases 4

Common Pitfalls to Avoid

Misdiagnosis as Bacterial Acne

• Fungal acne is frequently misdiagnosed as acne vulgaris and treated inappropriately with antibiotics, which worsens the condition 3
• The monomorphic appearance and pruritus are key differentiating features that should prompt consideration of fungal etiology 1, 2

Failure to Recognize Dual Pathology

• Many patients have both bacterial acne AND fungal folliculitis simultaneously 4
• Complete resolution requires treating both conditions—antifungals for the yeast and appropriate acne medications for the bacterial component 4

Seasonal and Activity-Related Fluctuations

• Symptoms often wax and wane with patient activities, time of year, and current treatments 4
• Heat, humidity, and occlusive clothing can exacerbate fungal overgrowth 3

Treatment Response as a Diagnostic Clue

• Dramatic improvement with antifungal therapy (oral: 92% success rate; topical: 81.6% success rate) confirms the diagnosis 2
• Most commonly used treatment is ketoconazole shampoo, which leads to improvement or resolution in most cases 1
• Some patients require oral azole antifungals (ketoconazole, itraconazole, fluconazole) for complete clearance 1, 4
• Rapid clinical response to antifungals distinguishes this from bacterial acne 3

Patient Demographics

• Predominantly affects younger males (64% male, average age 24 years) 2
• However, can occur in any age group or gender, particularly in adolescents with acne 4