Evaluation and Treatment of Abnormal Fingernails in Children
Diagnostic Approach
Always obtain mycological confirmation before initiating treatment, as 50% of dystrophic nails in children are non-fungal despite similar clinical appearance. 1, 2
Essential Diagnostic Steps
- Perform direct microscopy with potassium hydroxide (KOH) preparation and fungal culture on Sabouraud's glucose agar to confirm fungal infection before starting antifungal therapy 2, 3
- Calcofluor white staining enhances visualization of fungal elements and improves diagnostic accuracy 2
- Examine the entire family (parents and siblings) for onychomycosis and tinea pedis, as household transmission is common 2
- Check for concomitant infections including tinea capitis and tinea pedis in the affected child 2
- Perform complete physical examination of skin and oral mucosa, as systemic diseases can manifest with nail changes 4
Key Clinical Patterns in Children
- Distal and lateral subungual onychomycosis is the most common presentation in pediatric patients 1
- Superficial white onychomycosis appears as white lesions on the nail surface, particularly toenails, gradually spreading until the entire nail plate is involved—this form is most commonly seen in children and usually caused by T. interdigitale 1
- T. rubrum is the most prevalent causative organism (64% of cases), followed by T. tonsurans 1
- Onychomycosis in children often occurs with occlusive footwear and represents 15% of all nail dystrophies in this age group 1
Treatment Algorithm
First-Line Systemic Therapy for Confirmed Dermatophyte Infection
Terbinafine is the preferred first-line treatment for dermatophyte onychomycosis in children, with superior efficacy over other agents. 1, 5
Terbinafine Dosing (Weight-Based)
Duration:
Expected cure rates: 88% overall, with pediatric patients demonstrating higher cure rates and faster response than adults 2
Monitoring: Baseline liver function tests and complete blood count are recommended, as terbinafine is unlicensed for pediatric use in some jurisdictions 1
Alternative First-Line: Itraconazole Pulse Therapy
Itraconazole pulse therapy is equally effective as first-line treatment and particularly useful when Candida species are suspected. 1, 5, 2
Itraconazole Pulse Dosing
- 5 mg/kg/day for 1 week per month 1, 2
- Fingernails: 2 pulses (2 months total) 1, 2
- Toenails: 3 pulses (3 months total) 1, 2
Expected cure rates: 94-100% clinical cure for confirmed fungal infection 2
Administration: Take with food and acidic pH for optimal absorption 1
Monitoring: Check hepatic function tests in patients with pre-existing abnormalities, those receiving continuous therapy >1 month, or with concomitant hepatotoxic drugs 1
Contraindications: Heart failure, hepatotoxicity 1
Second-Line Options
Fluconazole
- Dosing: 3-6 mg/kg once weekly 1
- Duration: 12-16 weeks (fingernails), 18-26 weeks (toenails) 1
- Use when: Itraconazole and terbinafine are contraindicated or not tolerated 1
- Monitoring: Baseline liver function tests and complete blood count; monitor LFTs with high-dose or prolonged therapy 1
Griseofulvin
- Dosing: 10 mg/kg/day (maximum 500 mg) for children ≥1 month 1, 3
- Duration: Fingernails at least 4 months, toenails at least 6 months 3
- Administration: Take with fatty food to increase absorption 1, 3
- Limitations: Lower efficacy and higher relapse rates compared to terbinafine and itraconazole 1
- Use when: Itraconazole and terbinafine are contraindicated or not tolerated 1
Topical Therapy
Topical agents are inferior to systemic therapy except for very distal infection or superficial white onychomycosis. 5
Topical Options
- Amorolfine 5% lacquer: Apply once or twice weekly for 6-12 months 1, 5
- Ciclopirox 8% lacquer: Apply daily for up to 48 weeks 1, 5
- Tioconazole 28% solution: Apply twice daily for 6-12 months 1
Best use: As adjunct to systemic therapy for improved cure rates 5
Non-Fungal Causes to Consider
Bacterial Infection (Green Nail Syndrome)
- Caused by Pseudomonas aeruginosa or Proteus species 6, 2
- Treatment: Keep area dry and apply topical povidone iodine 2% twice daily 6, 2
Inflammatory Conditions
- Psoriasis and lichen planus can cause nail thinning and longitudinal ridging 6
- Treatment for <3 nails affected: Intralesional triamcinolone acetonide 5-10 mg/cc for nail matrix involvement; topical steroids ± vitamin D analogs for nail bed involvement 6
Chronic Paronychia
- Occurs in children due to thumb sucking or chronic moisture exposure 1
- Leads to proximal nail dystrophy with swelling of posterior nail fold 1, 6
Critical Management Principles
- Never start antifungal treatment without laboratory confirmation, as this leads to unnecessary therapy for non-fungal nail dystrophies 5, 2
- Complete the full treatment duration to prevent relapse—inadequate treatment results in 25% relapse rates 5
- Follow-up for minimum 48 weeks from treatment start to detect relapse and confirm cure 5
- Preventive measures: Apply regular antifungal powder inside shoes and periodic terbinafine solution spraying into shoes 5
- Daily topical emollients to cuticles and periungual tissues help prevent nail problems 6
Common Pitfalls to Avoid
- Assuming fungal infection based on appearance alone—50% of dystrophic nails are non-fungal 2
- Failing to examine family members for fungal infections, missing household transmission 2
- Stopping treatment prematurely before complete eradication of the organism 3
- Ignoring drug interactions, particularly itraconazole with statins, antiretrovirals, and in heart failure patients 5
- Not monitoring liver function in patients on prolonged systemic antifungal therapy 1