What are the clinical manifestations of tinea pedis in pediatric patients with toenail involvement?

Clinical Manifestations of Tinea Pedis with Toenail Involvement in Pediatric Patients

Children with tinea pedis and toenail involvement most commonly present with distal and lateral subungual onychomycosis (DLSO) characterized by thickened, discolored nails with onycholysis, accompanied by interdigital or inflammatory foot lesions that may be misdiagnosed as bacterial cellulitis. 1

Primary Nail Manifestations

Distal and Lateral Subungual Onychomycosis (DLSO) is the predominant presentation in pediatric patients with toenail involvement:

• The toenails become thickened and discolored with varying degrees of onycholysis (separation of the nail plate from the nail bed) 1
• The fungus invades by penetrating the distal or lateral margins of the nail 1
• T. rubrum is the most prevalent causative organism (64% of cases), followed by T. mentagrophytes 2
• Toenails are more commonly affected than fingernails in children 1

Superficial White Onychomycosis (SWO) may also occur:

• White crumbling lesions appear on the nail surface, particularly toenails, gradually spreading until the entire nail plate is involved 1
• This presentation is most commonly seen in children and is usually caused by T. interdigitale infection 1, 2
• The infection begins at the superficial layer and spreads to deeper layers 1

Concomitant Foot Manifestations

Interdigital Tinea Pedis frequently accompanies nail involvement:

• Standard interdigital presentation with scaling, maceration, and fissuring between toes 3
• May be asymptomatic or cause mild discomfort 3

Inflammatory/Bullous Tinea Pedis can masquerade as bacterial cellulitis:

• Presents with erythema, edema, and bullae formation that mimics bacterial infection 4, 5
• This inflammatory presentation is more common than previously recognized in children and is frequently misdiagnosed 4
• Potassium hydroxide (KOH) examination is essential to distinguish from cellulitis 4, 5
• Both T. rubrum and T. interdigitale can cause bullous presentations in children 5

Critical Diagnostic Features to Examine

Nail-Specific Findings:

• Soft, friable texture of the nail plate (distinguishes fungal infection from non-infectious causes) 6
• Subungual hyperkeratosis (thickening under the nail) 1
• Discoloration ranging from white to yellow-brown 1
• The nail surface becomes soft and friable, unlike non-infectious dystrophies 2

Associated Skin Findings:

• Examine carefully for concomitant tinea capitis and tinea pedis elsewhere on the body 1
• Check for inflammatory eruptions on the feet that may represent dermatophyte infection rather than bacterial cellulitis 4, 5
• Look for scaling, erythema, or vesiculation in interdigital spaces 3

Family and Household Considerations

Examine all household contacts:

• Parents and siblings should be checked for onychomycosis and tinea pedis, as familial disease commonly occurs 1, 7, 8
• Concomitant dermatophytosis at other body locations is confirmed in 25% of pediatric onychomycosis cases 2
• Failing to treat all infected family members simultaneously results in reinfection 3

Common Diagnostic Pitfalls

Do not diagnose based on appearance alone:

• 50% of nail dystrophy cases in children are non-fungal despite similar clinical presentation 2
• Always obtain mycological confirmation with KOH preparation and fungal culture on Sabouraud's glucose agar before initiating treatment 2, 8
• Calcofluor white staining enhances visualization of fungal elements 2

Do not overlook inflammatory presentations:

• Inflammatory tinea pedis/manuum can masquerade as bacterial cellulitis in children 4
• Early KOH examination allows appropriate antifungal treatment before culture results are finalized 4
• A potassium hydroxide test and fungal culture should always be performed when examining a child with inflammatory eruption of the feet 5

Associated Complications and Quality of Life Impact

Physical complications:

• Discomfort and difficulty wearing footwear 1
• Infected nails serve as a reservoir for spread to hands, feet, and groin 1
• Risk of secondary bacterial infection, particularly in diabetic or immunocompromised children 1

Psychosocial impact:

• Cosmetic embarrassment and lowered self-esteem 1
• Approximately 50% of patients experience pain or discomfort 1
• About 30% have difficulty wearing footwear 1