Dermatophyte Infections

Introduction | Aetiology and Risk Factors | Clinical Presentation | Diagnosis | Management and Treatment | Prevention | When to Refer | References

Introduction

Dermatophyte infections, also known as tinea infections or ringworm, are superficial fungal infections that affect the skin, hair, and nails. These infections are caused by dermatophytes, a group of fungi that can digest keratin, the protein found in skin, hair, and nails. Dermatophyte infections are commonly named according to the body part they affect, such as tinea pedis (athlete's foot), tinea corporis (body ringworm), tinea capitis (scalp ringworm), and tinea unguium (nail infection or onychomycosis).

Aetiology and Risk Factors

Dermatophyte infections are caused by various species of dermatophytes, most commonly belonging to three genera: Trichophyton, Microsporum, and Epidermophyton. Key risk factors include:

• Warm, Moist Environments: Dermatophytes thrive in warm, moist conditions, making environments such as public showers, swimming pools, and locker rooms common sources of infection.
• Direct Contact: The infection can spread through direct contact with an infected person, animal, or contaminated objects such as towels, clothing, and grooming tools.
• Compromised Immunity: Individuals with weakened immune systems, such as those with diabetes or HIV, are more susceptible to dermatophyte infections.
• Close Living Conditions: Living in crowded or communal settings increases the risk of transmission.
• Occupational Exposure: Individuals who work in environments where they are frequently exposed to soil, animals, or people with dermatophyte infections are at higher risk.

Clinical Presentation

The clinical presentation of dermatophyte infections varies depending on the affected area of the body:

• Tinea Pedis (Athlete’s Foot): Characterised by itching, scaling, and fissuring between the toes. The soles of the feet may also become red and scaly.
• Tinea Corporis (Body Ringworm): Presents as circular or oval, red, scaly patches with a raised border, often with central clearing. These lesions can occur anywhere on the body.
• Tinea Capitis (Scalp Ringworm): Common in children, this infection leads to scaly patches on the scalp, sometimes with hair loss and broken hairs. Inflammatory forms can cause kerion, a painful, swollen mass.
• Tinea Cruris (Jock Itch): Occurs in the groin area, presenting as red, itchy, and often scaly lesions. It may extend to the inner thighs and buttocks.
• Tinea Unguium (Onychomycosis): Affects the nails, leading to thickening, discoloration, and crumbling of the nail. Toenails are more commonly affected than fingernails.
• Tinea Manuum: Affects the hands, causing dry, scaly, and sometimes itchy patches, often affecting only one hand.
• Tinea Barbae: Affects the beard area, leading to redness, scaling, and sometimes pustules or nodules.

Diagnosis

Diagnosis of dermatophyte infections is typically clinical but may be confirmed with laboratory tests:

• History: Take a thorough history, including onset and duration of symptoms, potential exposures, and any previous treatments.
• Physical Examination: Examine the affected areas for characteristic signs of dermatophyte infection, such as ring-shaped lesions, scaling, and nail changes.
• Microscopy: Skin scrapings, nail clippings, or hair samples can be examined under a microscope after treatment with potassium hydroxide (KOH) to identify fungal elements.
• Fungal Culture: A culture can be performed to identify the specific species of dermatophyte, which may guide treatment in resistant or recurrent cases.
• Wood’s Lamp: A Wood’s lamp (UV light) may be used in some cases, particularly for tinea capitis, where some species of Microsporum fluoresce under UV light.

Management and Treatment

Management of dermatophyte infections involves the use of antifungal medications, good hygiene practices, and addressing any underlying conditions that may predispose to infection:

1. Topical Antifungals

• Topical Azoles: Clotrimazole, miconazole, and ketoconazole creams are commonly used for treating localized dermatophyte infections such as tinea corporis, tinea cruris, and tinea pedis. They are typically applied twice daily for 2-4 weeks.
• Terbinafine: A topical allylamine antifungal, terbinafine is effective for treating dermatophyte infections and may be used once or twice daily, depending on the product, for 1-2 weeks.

2. Oral Antifungals

Oral antifungal therapy is indicated for more extensive infections, tinea capitis, tinea unguium, or when topical treatment has failed:

• Terbinafine: The first-line oral treatment for onychomycosis and tinea capitis, terbinafine is usually taken daily for 6 weeks for fingernail infections and 12 weeks for toenail infections. Tinea capitis treatment typically lasts for 4-6 weeks.
• Itraconazole: An alternative to terbinafine, itraconazole is used in pulse dosing or continuous dosing for onychomycosis and other resistant dermatophyte infections.
• Griseofulvin: An older antifungal used mainly for tinea capitis, particularly in children. Treatment duration is usually 6-8 weeks, depending on the severity.
• Fluconazole: Sometimes used as an alternative for various dermatophyte infections, particularly when other treatments are not suitable.

3. Supportive Care

• Good Hygiene Practices: Encourage patients to keep affected areas clean and dry, avoid sharing personal items, and wear breathable clothing to reduce moisture build-up.
• Nail Care: For onychomycosis, advise regular trimming and filing of nails, and consider the use of antifungal nail lacquers for adjunctive therapy.
• Foot Care: For tinea pedis, recommend using antifungal powders and avoiding walking barefoot in communal areas like showers and changing rooms.

Prevention

Preventive measures are essential to reduce the risk of dermatophyte infections and prevent recurrence:

• Avoid Sharing Personal Items: Discourage the sharing of towels, shoes, and grooming tools, which can spread infection.
• Maintain Good Hygiene: Regularly wash and thoroughly dry the skin, particularly after sweating or exposure to moisture.
• Use Antifungal Products: In recurrent cases, prophylactic use of antifungal powders or sprays in shoes and on feet can be beneficial.
• Protective Footwear: Wear flip-flops or sandals in communal showers, swimming pools, and locker rooms to reduce exposure to dermatophytes.

When to Refer

Referral to a dermatologist may be necessary in the following situations:

• Refractory Cases: If the infection does not respond to standard treatments, referral for further evaluation and management is advised.
• Extensive or Severe Infection: For extensive infections or those that affect multiple body sites, specialist care may be required.
• Uncertain Diagnosis: If the diagnosis is unclear or if there are concerns about other underlying conditions, a dermatologist's input may be necessary.
• Complications: In cases where secondary bacterial infection, significant discomfort, or other complications arise, specialist input is advised.

References

1. British Association of Dermatologists (2024) Guidelines for the Management of Dermatophyte Infections. Available at: https://www.bad.org.uk (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (2024) Dermatophyte Infections: Diagnosis and Management. Available at: https://www.nice.org.uk/guidance/ng104 (Accessed: 26 August 2024).
3. British National Formulary (2024) Topical and Oral Treatments for Dermatological Conditions. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).