In a 1‑month‑old infant with a 4 cm round scalp lesion with rolled edges and purulent drainage, what is the diagnosis and appropriate treatment including dosage?

Kerion Celsi (Inflammatory Tinea Capitis) with Secondary Bacterial Infection

This 1-month-old infant most likely has kerion celsi (severe inflammatory tinea capitis) with secondary bacterial superinfection, requiring immediate systemic antifungal therapy combined with antibiotics targeting Staphylococcus aureus.

Diagnosis

The clinical presentation—a 4 cm round scalp lesion with rolled edges and purulent drainage in an infant—is pathognomonic for kerion celsi. This represents a severe host inflammatory response to dermatophyte infection 1. The purulent component indicates bacterial superinfection, most commonly with S. aureus, which frequently complicates kerion 2.

Key diagnostic steps:

• Obtain fungal culture and KOH preparation from plucked hairs and scale
• Bacterial culture and Gram stain of purulent drainage 3
• Consider Wood's lamp examination (though many causative organisms don't fluoresce)
• PCR-ELISA can provide rapid diagnosis if available 2

Common causative fungi in infants include Microsporum canis (from animal contact) 4 and Trichophyton species 2.

Treatment Protocol

Antifungal Therapy (Primary Treatment)

Oral fluconazole 5 mg/kg/day is the recommended first-line agent for neonatal/infant kerion 2, 4. This dosing was specifically effective in documented infant cases with complete resolution.

Alternative options:

• Griseofulvin: Standard agent but requires longer treatment (6-8 weeks) 5, 6
• Itraconazole: Effective alternative 5

Duration: Minimum 4 weeks, continuing until clinical resolution and negative cultures 2, 5

Antibiotic Therapy (For Bacterial Superinfection)

Given the purulent drainage, empiric antibiotics targeting S. aureus are mandatory 3:

For outpatient management (if systemically well):

• Cephalexin 25-50 mg/kg/day divided every 6-8 hours OR
• Dicloxacillin 12.5-25 mg/kg/day divided every 6 hours 3

If MRSA suspected or confirmed:

• Clindamycin 10-13 mg/kg/dose every 6-8 hours OR
• Trimethoprim-sulfamethoxazole 8-12 mg/kg/day (TMP component) divided every 12 hours 3

Duration: 7 days 3

When to Hospitalize

Consider intravenous therapy if the infant shows:

• Systemic signs (fever >38°C, irritability, poor feeding)
• Failed outpatient therapy
• Extensive lesions
• Age <1 month (this patient is at the threshold)

In such cases, use vancomycin 15 mg/kg/dose every 6-8 hours plus fosfomycin as documented effective in a similar infant case 2.

Surgical Intervention

Incision and drainage is NOT routinely recommended for kerion, unlike typical abscesses 3. The purulent material in kerion is inflammatory exudate, not a true abscess. However, if a discrete abscess pocket forms, drainage may be necessary 2.

Critical Monitoring

• Liver function tests at baseline and every 2 weeks during antifungal therapy 4
• Clinical response assessment weekly
• Repeat fungal cultures after 2-4 weeks to confirm clearance

Common Pitfalls to Avoid

1. Treating with antibiotics alone: This will not address the underlying fungal infection and leads to treatment failure 2
2. Using only topical antifungals: Systemic therapy is mandatory as topicals cannot penetrate hair shafts 6
3. Delaying treatment: Early intervention prevents permanent scarring alopecia 1, 5
4. Misdiagnosing as bacterial infection only: The rolled edges and inflammatory nature suggest fungal etiology with secondary bacterial infection

Expected Outcome

With appropriate dual therapy, expect near-complete resolution within 4 weeks 2. Without prompt treatment, permanent scarring alopecia is likely 1, 5.