What is the treatment for a patient with Trichophyton rubrum (dermatophyte) isolated, likely suffering from tinea pedis (athlete's foot), tinea corporis (ringworm of the body), or onychomycosis (fungal infection of the nails)?

Treatment of Trichophyton rubrum Infection

For T. rubrum infections, treatment depends critically on the anatomical site involved: use topical terbinafine 1% cream twice daily for 1 week for tinea pedis, topical antifungals for 2-4 weeks for tinea corporis, and oral terbinafine 250 mg daily for 12 weeks for toenail onychomycosis. 1, 2, 3

Clinical Context and Diagnosis

T. rubrum is the causative organism in over 90% of dermatophyte onychomycosis cases and is the predominant pathogen in tinea pedis and tinea corporis. 2 Before initiating any systemic therapy, mycological confirmation through KOH preparation, fungal culture, or nail biopsy is mandatory, as 50% of dystrophic nails are non-fungal despite similar clinical appearance. 2, 4, 3

Key Diagnostic Considerations:

• Examine all body sites, as concomitant dermatophytosis occurs in 25% of cases, particularly hands, groin, and body folds 4, 1
• Screen household members, as familial transmission is the most common route of infection 4
• Look for evidence of tinea pedis when fingernail dermatophytosis is present, as toenail infection is an almost inevitable precursor 2

Treatment by Anatomical Site

Tinea Pedis (Athlete's Foot)

First-line topical therapy:

• Terbinafine 1% cream applied twice daily for 1 week is the most effective topical treatment, superior to longer courses of other antifungals 1, 4
• Ciclopirox olamine 0.77% cream/gel twice daily achieves approximately 60% clinical cure at end of treatment and 85% two weeks after treatment 1, 4
• Clotrimazole 1% cream is less effective than terbinafine but widely available over-the-counter 1

Oral therapy indications (reserve for severe disease, failed topical therapy, concomitant onychomycosis, or immunocompromised patients): 1, 5

• Terbinafine 250 mg once daily for 1-2 weeks (first-line systemic option with fungicidal action) 1, 2
• Itraconazole 100 mg daily for 2 weeks or pulse dosing 200-400 mg per day for 1 week per month 1, 2
• Fluconazole is less effective than terbinafine or itraconazole but may be used when others are contraindicated due to fewer drug interactions 1

Tinea Corporis (Ringworm of the Body)

Topical antifungals for 2-4 weeks are typically sufficient for localized disease. 6 The same topical agents effective for tinea pedis (terbinafine, ciclopirox, clotrimazole) can be used. 1 Oral therapy with terbinafine or itraconazole should be reserved for extensive or treatment-resistant cases. 2

Onychomycosis (Nail Infections)

Oral terbinafine is the first-line treatment for dermatophyte onychomycosis:

• Terbinafine 250 mg daily for 12 weeks continuously for toenails 2, 7, 3
• Fingernails require at least 4 months; toenails require at least 6 months for complete clearance 6
• Baseline liver function tests and complete blood count are required before initiating therapy 7
• Monitor liver function tests for patients receiving continuous therapy >1 month 4

Alternative oral regimens:

• Itraconazole 200 mg per day for 12 weeks continuously, or pulse dosing (200 mg twice daily for 1 week per month, repeated for 3-4 months for toenails) 2
• Griseofulvin is not recommended as first-line therapy due to lower efficacy (30-40% cure rates) and longer treatment duration 1, 6

Important caveat: Dermatophytomas (dense white lesions of tightly packed hyphae visible beneath the nail) can be resistant to antifungal treatment without prior mechanical removal. 2 Nail thickness >2 mm, severe onycholysis, and dermatophytoma contribute to treatment failure. 2

Special Populations

Diabetic Patients

Terbinafine is preferred over itraconazole due to lower risk of drug interactions and hypoglycemia, which is particularly important as up to one-third of diabetics have onychomycosis. 4 Diabetics have higher risk of complications from onychomycosis, including bacterial superinfection and limb-threatening complications. 2

Pediatric Patients

• Terbinafine is the preferred first-line systemic treatment 4
• Weight-based dosing: 62.5 mg daily if <20 kg, 125 mg daily for 20-40 kg, 250 mg daily if >40 kg 4
• Topical terbinafine 1% cream twice daily for 1 week for interdigital tinea pedis 4
• Monitor for at least 48 weeks from treatment start to identify potential relapse 4

Immunocompromised Patients

Proximal subungual onychomycosis without paronychia is uncommon and often related to immunosuppression (HIV-positive patients, transplant recipients, those on immunosuppressive treatments). 2 These patients require systemic therapy and may have more widespread disease. 2

Prevention Strategies to Prevent Recurrence

Environmental and hygiene measures are critical, as T. rubrum is commonly found in hotel bedrooms, carpeting, gyms, and changing rooms: 2

• Discard old, moldy footwear or decontaminate by placing naphthalene mothballs in shoes and sealing in a plastic bag for minimum 3 days 2, 7
• Apply antifungal powders (miconazole, clotrimazole, or tolnaftate) inside shoes daily or spray terbinafine solution periodically 2, 4, 7
• Wear cotton, absorbent socks and change daily 2, 7
• Wear protective footwear in public bathing facilities, gyms, hotel rooms, and locker rooms 2, 4, 7
• Keep nails trimmed short and avoid sharing nail clippers 2, 7
• Cover active foot lesions with socks before wearing underwear to prevent spread to groin 1, 4
• Treat all infected family members simultaneously to prevent reinfection 2, 1
• Thoroughly dry between toes after showering 1

Common Pitfalls to Avoid

• Failing to obtain mycological confirmation before treatment leads to unnecessary systemic therapy for non-fungal conditions 2, 4
• Not examining for concomitant onychomycosis when treating tinea pedis, as nail infection serves as a reservoir for reinfection 1
• Inadequate treatment duration for onychomycosis—up to 18 months is required for complete toenail replacement 2
• Ignoring contaminated footwear as a source of reinfection 2, 1
• Prescribing oral therapy without considering drug interactions, particularly important with itraconazole which has significant cytochrome P450 interactions 1
• Not treating household members, leading to reinfection cycles 2, 1

Treatment Failure vs. Relapse

Recurrence rates of 40-70% are reported for onychomycosis. 2 True treatment failure occurs when infection is not completely cured due to:

• Carriage of arthroconidia and chlamydoconidia (resting fungal elements) in the nail plate 2
• Presence of dermatophytomas requiring mechanical removal 2
• Nail thickness >2 mm or severe onycholysis 2

Reinfection occurs after complete cure through re-exposure to contaminated environments, emphasizing the critical importance of prevention strategies outlined above. 2