Onychomycosis — SCE Dermatology MCQ

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EasyCutaneous InfectionOnychomycosisSCE Dermatology

A 25-year-old man has onychomycosis. His GP wants to start oral Terbinafine but is unsure whether mycological confirmation is needed before prescribing. According to BAD guidelines, is mycological confirmation required?

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Correct answer: C — Yes — mycological confirmation (KOH microscopy and/or culture) is recommended before starting systemic antifungal therapy

BAD guidelines recommend mycological confirmation (KOH direct microscopy showing fungal elements and/or positive dermatophyte culture) before starting systemic antifungal therapy for onychomycosis. This is important because: (1) only approximately 50% of clinically suspected onychomycosis is confirmed mycologically; (2) systemic antifungals have potential side effects and drug interactions requiring justified use; (3) differential diagnoses (psoriasis, lichen planus, traumatic onychodystrophy) require different management. Nail clippings for microscopy and culture should be taken from the most proximal area of abnormal nail. A negative result may need repeating if clinical suspicion is high (false negative rate ~30%).

Reference: BAD 2014 Onychomycosis Guidelines; NICE CKS