A 10-year-old presents with hypopigmented macules over the trunk. KOH examination of scrapings shows 'spaghetti and meatballs' pattern. What is the causative organism and the MOST appropriate systemic treatment if topical therapy fails?
- A Malassezia furfur; oral fluconazole 400 mg single dose
- B Malassezia furfur (or M. globosa); oral itraconazole 200 mg/day for 7 days ✓
- C Trichophyton rubrum; oral terbinafine 250 mg/day for 2 weeks
- D Pityrosporum ovale; oral ketoconazole 200 mg/day for 4 weeks
Explanation
Pityriasis versicolor (tinea versicolor) is caused by Malassezia furfur (previously called Pityrosporum ovale/orbiculare) — the current taxonomy recognizes M. globosa and M. furfur as the dominant species. KOH shows the classic 'spaghetti and meatballs' (hyphae + yeast cells = clusters of short curved hyphae with round spores). Topical antifungals (selenium sulfide, ketoconazole shampoo, clotrimazole) are first-line. For extensive disease or failure of topical therapy, systemic itraconazole 200 mg/day for 5–7 days is the most appropriate option, with excellent bioavailability in sebaceous glands. Fluconazole 400 mg single dose is an alternative but 200 mg is used more reliably. Terbinafine has poor efficacy against Malassezia because it has minimal sebaceous secretion.
Reference: Ghai Essential Pediatrics, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.