Onychomycosis and Fungal Infections Flashcards

The most common causative organism of onychomycosis is:

Answer: Trichophyton rubrum

Trichophyton rubrum is the most prevalent dermatophyte causing onychomycosis worldwide, accounting for approximately 70% of cases.

Distal-lateral subungual onychomycosis (DLSO) characteristically begins at the:

Answer: Distal and lateral nail bed, progressing proximally

DLSO is the most common clinical pattern, starting at the hyponychium (distal nail bed) and spreading proximally beneath the nail plate.

Which clinical sign distinguishes proximal subungual onychomycosis (PSO) from other types?

Answer: White opacity beginning at the proximal nail plate near the cuticle

PSO presents with white/opaque discoloration at the proximal nail, near the cuticle, as fungi enter through the proximal nail fold; it is often associated with immunosuppression.

Nail debridement in onychomycosis management primarily aims to:

Answer: Reduce fungal load and improve topical antifungal penetration to the nail bed

Mechanical debridement removes infected nail material, reducing fungal burden and allowing topical agents to penetrate more deeply to the infection site.

KOH (potassium hydroxide) preparation is used in onychomycosis diagnosis to:

Answer: Dissolve keratin and visualize fungal hyphae microscopically

KOH dissolves keratin without destroying fungal cell walls, allowing microscopic visualization of hyphae, pseudohyphae, or spores to confirm fungal infection.

White superficial onychomycosis (WSO) is characterized by:

Answer: Chalky-white patches on the dorsal nail plate surface that scrape off easily

WSO affects only the surface of the nail plate, presenting as white, powdery or chalky patches that can be scraped off; it is most commonly caused by T. mentagrophytes.