Characteristics of Fungal Rash in the Armpit
A fungal rash in the armpit typically presents as a well-demarcated, erythematous patch with a raised, scaling border and central clearing, often with satellite lesions and intense pruritus. 1
Clinical Presentation
Primary Features
- Appearance: Erythematous (red), well-demarcated patches or plaques
- Border characteristics: Raised, scaling, active border that may be more pronounced than the center
- Central clearing: Often shows central clearing giving a ring-like or annular appearance
- Distribution: Typically bilateral but can be asymmetric
- Associated symptoms: Intense itching (pruritus) is common
Secondary Features
- Satellite lesions: Small papules or pustules beyond the main border
- Maceration: Skin may appear soggy or whitish in moist areas
- Hyperpigmentation: Brown discoloration may develop, especially in darker skin tones
- Excoriation marks: Due to scratching from intense itching
Differential Diagnosis
Several conditions may mimic a fungal rash in the armpit:
- Erythrasma: Bacterial infection caused by Corynebacterium minutissimum, appears as brown-red patches with fine scaling
- Intertrigo: Non-infectious inflammatory condition in skin folds
- Contact dermatitis: Reaction to deodorants, clothing, or other irritants
- Seborrheic dermatitis: Greasy scaling with less distinct borders
- Inverse psoriasis: Smooth, red patches without the typical scaling of psoriasis
Diagnostic Features
Visual Examination
- Look for the classic "ring-like" appearance with active border and central clearing
- Assess for bilateral involvement (common in fungal infections)
- Check for satellite lesions which strongly suggest fungal etiology
Diagnostic Tests
- KOH preparation: Scraping from the active border examined under microscope with potassium hydroxide shows branching hyphae 1
- Wood's lamp examination: Some fungal infections may fluoresce, though tinea infections typically do not
- Fungal culture: Can identify specific fungal species for resistant cases
Common Causative Organisms
- Trichophyton rubrum: Most common cause
- Trichophyton mentagrophytes: Second most common
- Candida species: More common in immunocompromised patients or diabetics
- Malassezia furfur: Can cause a variant called tinea versicolor
Complications and Special Considerations
- Bacterial superinfection: Can occur with excessive scratching
- Spread to other body areas: Without treatment, infection can spread
- Recurrence: Common if treatment is inadequate or predisposing factors persist
- Resistance: Increasing prevalence of antifungal-resistant strains, particularly to terbinafine 2
Risk Factors
- Obesity: Creates warm, moist environment favorable for fungal growth
- Diabetes: Increases susceptibility to fungal infections
- Immunosuppression: HIV, medications, or other conditions that compromise immunity
- Hyperhidrosis: Excessive sweating creates ideal environment for fungi
- Tight clothing: Reduces airflow and increases moisture retention
By recognizing these characteristic features, clinicians can accurately diagnose fungal rashes in the armpit and distinguish them from other similar-appearing conditions, leading to appropriate treatment and improved outcomes.