In a 60-year-old male with a one-month-old, 4 cm round, infected lesion with raised edges on the frontal scalp, what is the most likely diagnosis and appropriate treatment including dosage?

Diagnosis and Treatment

This is a kerion, a severe inflammatory form of tinea capitis (scalp ringworm), and requires oral griseofulvin 500-1000 mg daily (or 20-25 mg/kg/day) for 6-8 weeks, plus adjunctive antifungal shampoo and consideration of empiric antibiotics if secondary bacterial infection is suspected.

Diagnosis: Kerion Celsi

The clinical presentation—a 4 cm round, infected lesion with raised edges on the scalp in a 60-year-old male—is classic for kerion, not bacterial cellulitis or abscess. While kerion is more common in children, it does occur in adults and frequently mimics bacterial infection, leading to misdiagnosis and inappropriate antibiotic-only treatment 1, 2. The key distinguishing features are:

• Round configuration with raised, inflammatory borders
• One-month duration (bacterial infections typically evolve faster)
• Scalp location with likely associated hair loss
• "Infected" appearance with possible pustulation

Critical pitfall: Kerion is commonly mistaken for bacterial furunculosis or abscess in adults, resulting in delayed antifungal treatment and potential permanent scarring 1, 2.

Immediate Diagnostic Confirmation

Before or immediately after starting treatment:

• Obtain KOH preparation (potassium hydroxide examination) for immediate microscopy—can show fungal elements within hours
• Send fungal culture (results take 2-4 weeks but identify specific organism)
• Do not delay treatment while awaiting culture results given the severity and risk of scarring 3

Treatment Protocol

Primary Systemic Antifungal Therapy

Griseofulvin remains the gold standard and only licensed treatment for tinea capitis in the UK 3:

• Dosage: 500-1000 mg daily (or 20-25 mg/kg/day for adults <50 kg)
• Duration: 6-8 weeks minimum
• Administration: Take with fatty food to enhance absorption
• May increase to 25 mg/kg/day for resistant cases 3

Alternative (unlicensed but effective): Terbinafine 250 mg daily for 4-6 weeks, though this remains unlicensed for scalp infections in many regions 3.

Adjunctive Topical Therapy

Antifungal shampoo to reduce spore transmission 3:

• Ketoconazole 2% shampoo, OR
• Selenium sulfide 1% shampoo, OR
• Povidone-iodine shampoo

Apply 2-3 times weekly throughout treatment course.

Secondary Bacterial Infection Coverage

Given the "infected" appearance with likely pustulation, consider empiric antibiotic coverage for secondary Staphylococcus aureus infection 1:

• Cephalexin 500 mg four times daily for 7-10 days, OR
• Dicloxacillin 500 mg four times daily for 7-10 days
• If MRSA risk factors present: Doxycycline 100 mg twice daily or trimethoprim-sulfamethoxazole DS twice daily

The recent case report showed clinical improvement with ciprofloxacin for suspected secondary infection 1, though anti-staphylococcal coverage is more appropriate.

Supportive Care

• Gentle wound care with saline cleansing
• Avoid manipulation or squeezing
• Pain management with NSAIDs or acetaminophen

Expected Clinical Course

• Periorbital edema (if present) should improve within 2-3 days 1
• Pain and pustulation should decrease within 2 weeks 1
• Complete resolution requires full 6-8 week antifungal course
• Permanent scarring alopecia can occur if treatment is delayed 3, 4

Key Clinical Distinctions

This is NOT:

• Bacterial cellulitis: Would require vancomycin or beta-lactam coverage per IDSA guidelines 5, but the chronic course and morphology favor fungal etiology
• Folliculitis decalvans: Occurs mainly on vertex/occiput, presents with follicular tufting 6
• Atypical mycobacterial infection: Consider only if history of scalp injections 7

The combination of round configuration, raised edges, one-month duration, and scalp location makes kerion the overwhelming diagnosis, requiring immediate systemic antifungal therapy to prevent permanent scarring.