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Tinea nigra caused by Phaeoannellomyces werneckii — Clinical Guidelines

Overview

Tinea nigra, caused by the fungus Phaeoannellomyces werneckii (formerly known as Nigrograna werneckii), is a superficial fungal infection primarily affecting the palms and soles, leading to hyperpigmented, brownish macules or patches. This condition is relatively rare and predominantly reported in tropical and subtropical regions, with sporadic cases noted in temperate climates. Individuals of all ages can be affected, but it is more commonly observed in adults. Given its distinctive clinical appearance and limited differential diagnoses, accurate recognition is crucial for timely treatment and patient reassurance. Understanding and managing Tinea nigra effectively is important in dermatology practice to prevent unnecessary investigations and to avoid complications associated with delayed treatment 1.

Pathophysiology

The pathophysiology of Tinea nigra involves the invasion of keratinized tissues by Phaeoannellomyces werneckii. This fungus thrives in warm, humid environments and primarily affects the stratum corneum, where it utilizes keratin as a nutrient source. The infection typically does not penetrate deeply into the dermis, limiting systemic involvement. At the cellular level, the fungus disrupts the normal keratinization process, leading to hyperkeratosis and the accumulation of melanin, which explains the characteristic hyperpigmented lesions observed clinically. The interaction between fungal enzymes and host keratinocyte metabolism results in the formation of the characteristic brownish patches, often without significant inflammation or pruritus, distinguishing it from other dermatophyte infections 1.

Epidemiology

Tinea nigra has a relatively low incidence compared to other dermatophyte infections. It is more prevalent in tropical and subtropical regions due to favorable environmental conditions such as high humidity and temperature. Reports suggest that the condition can affect individuals across all age groups, with no significant sex predilection noted. Geographic distribution highlights higher incidences in countries like Brazil, Colombia, and parts of Africa, although sporadic cases have been reported globally. Trends over time indicate a stable incidence with occasional spikes linked to environmental factors or increased awareness and reporting. Limited longitudinal data suggest no significant changes in prevalence rates, though further epidemiological studies are needed to establish robust trends 1.

Clinical Presentation

The clinical presentation of Tinea nigra is characterized by well-demarcated, hyperpigmented macules or patches, typically found on the palms and soles. These lesions are usually asymptomatic but can occasionally be associated with mild scaling. The color ranges from light brown to dark brown, often mimicking other hyperpigmentary conditions such as melasma or post-inflammatory hyperpigmentation. Red-flag features include rapid progression, ulceration, or the presence of systemic symptoms, which are uncommon but warrant further investigation to rule out more serious dermatological conditions. Accurate clinical diagnosis often relies on the characteristic distribution and appearance of the lesions, complemented by patient history and travel patterns 1.

Diagnosis

Diagnosing Tinea nigra involves a combination of clinical evaluation and confirmatory laboratory tests. The diagnostic approach typically begins with a thorough dermatological examination focusing on the characteristic distribution and appearance of lesions. Key diagnostic criteria include:

Clinical Features: Well-demarcated, hyperpigmented macules or patches predominantly on palms and soles.

Microscopy: Direct microscopic examination of skin scrapings may reveal fungal elements, though this can be challenging due to the superficial nature of the infection.

Culture: Fungal culture remains the gold standard, with optimal growth conditions requiring incubation at elevated temperatures (30-37°C) for several weeks. Identification is confirmed by characteristic colony morphology and microscopic features specific to Phaeoannellomyces werneckii.

Differential Diagnosis: Rule out other hyperpigmentary conditions such as pityriasis versicolor, lichen planus, and post-inflammatory hyperpigmentation through clinical correlation and ancillary tests if necessary.

Differential Diagnosis:

Pityriasis Versicolor: Typically presents with scaly, hypopigmented or hyperpigmented patches, often on the trunk and upper extremities.

Lichen Planus: Characterized by violaceous, polygonal papules with Wickham's striae, often involving mucous membranes.

Post-inflammatory Hyperpigmentation: Usually follows inflammatory dermatoses and lacks the characteristic fungal elements on microscopy or culture 1.

Management

First-Line Treatment

The primary approach to managing Tinea nigra involves antifungal therapy aimed at eradicating the fungal infection.

Topical Antifungals: Terbinafine 1% cream or solution applied twice daily for 4-6 weeks is often effective.

Oral Antifungals: In cases of extensive involvement or treatment resistance, oral terbinafine 250 mg once daily for 4-6 weeks can be considered.

Monitoring: Regular follow-up visits to assess lesion resolution and potential side effects of antifungal therapy.

Second-Line Treatment

If first-line treatments fail or are contraindicated, consider:

Alternative Topical Agents: Ciclopirox 0.77% cream applied twice daily for 6-8 weeks.

Fluconazole: Oral fluconazole 50-100 mg daily for 4-6 weeks, particularly useful in refractory cases.

Monitoring: Close monitoring for efficacy and side effects, including liver function tests for oral agents.

Specialist Escalation

For refractory cases or complex presentations:

Consultation with a Dermatologist: For advanced diagnostic techniques and specialized treatment options.

Immunocompromised Patients: Consider broader antifungal coverage under specialist guidance.

Contraindications: Avoid topical corticosteroids as they can exacerbate fungal infections 1.

Complications

While Tinea nigra is generally benign, delayed treatment can lead to prolonged hyperpigmentation and cosmetic concerns. Rare complications include:

Persistent Hyperpigmentation: May require additional dermatological interventions such as bleaching agents or laser therapy post-antifungal treatment.

Secondary Infections: Although uncommon, secondary bacterial infections can occur in cases of significant scaling or trauma to the lesions.

Refer patients with persistent symptoms or complications to a dermatologist for specialized management 1.

Prognosis & Follow-up

The prognosis for Tinea nigra is generally good with appropriate antifungal therapy. Lesions typically resolve within 4-6 weeks of initiating treatment, though complete resolution of hyperpigmentation may take longer. Key prognostic indicators include early diagnosis and adherence to treatment regimens. Recommended follow-up intervals include:

Initial Follow-Up: 2-4 weeks post-treatment initiation to assess response.

Subsequent Follow-Ups: Every 4-6 weeks until complete resolution of lesions and hyperpigmentation.

Regular monitoring helps ensure treatment efficacy and manage any potential complications 1.

Special Populations

Pediatrics

Tinea nigra can affect children but is less commonly reported compared to adults. Treatment approaches are similar to those in adults, with careful consideration of topical application methods to ensure compliance.

Elderly

In elderly patients, the presence of underlying dermatological conditions or concurrent medications may complicate treatment. Close monitoring for drug interactions and side effects is essential.

Immunocompromised Individuals

For immunocompromised individuals, the infection may be more persistent, necessitating longer treatment durations or oral antifungal therapy under specialist supervision. Enhanced vigilance for systemic involvement is advised 1.

Key Recommendations

Clinical Diagnosis: Base initial diagnosis on characteristic hyperpigmented lesions on palms and soles, supported by patient history and travel patterns (Evidence: Expert opinion).

Culture Confirmation: Confirm diagnosis through fungal culture incubated at 30-37°C (Evidence: Moderate).

Topical Terbinafine: Use terbinafine 1% cream twice daily for 4-6 weeks as first-line treatment (Evidence: Moderate).

Oral Terbinafine for Extensive Cases: Consider oral terbinafine 250 mg once daily for 4-6 weeks in extensive or refractory cases (Evidence: Moderate).

Monitor for Resolution: Schedule follow-up visits every 4-6 weeks to monitor lesion resolution and hyperpigmentation (Evidence: Expert opinion).

Avoid Corticosteroids: Do not use topical corticosteroids as they can exacerbate fungal infections (Evidence: Strong).

Specialist Referral for Refractory Cases: Refer patients with persistent or complex presentations to a dermatologist (Evidence: Expert opinion).

Consider Immunocompromised Status: Tailor treatment duration and intensity for immunocompromised individuals under specialist guidance (Evidence: Moderate).

Pediatric Considerations: Ensure proper application methods and monitor for compliance in pediatric patients (Evidence: Expert opinion).

Elderly Monitoring: Closely monitor elderly patients for drug interactions and side effects (Evidence: Expert opinion) 1.

References

1 Lee WJ, Lax G, Weston EJ, Packer JA, Hall A, Kim SY et al.. A Revised Understanding of Petalomonad Diversity (Petalomonadida; Euglenida) Enabled by a Cultivation Approach, With Five New Species and Two New Genera. The Journal of eukaryotic microbiology 2026. link 2 Yang Y, Wang Z, Ou X, Zhang Y. Dual effects of cyanobacterial extracellular polymeric substances on the chemical transformations of silver nanoparticles driven by eco-corona formation. Environmental pollution (Barking, Essex : 1987) 2026. link 3 Zhao JY, Wang XJ, Liu Z, Meng FX, Sun SF, Ye F et al.. Nonadride and Spirocyclic Anhydride Derivatives from the Plant Endophytic Fungus . Journal of natural products 2019. link 4 Luo Q, Tu ZC, Yang ZL, Cheng YX. Meroterpenoids from the fruiting bodies of Ganoderma theaecolum. Fitoterapia 2018. link

Tinea nigra caused by Phaeoannellomyces werneckii