A 60–year old male presented with discolouration, thickening and tunneling of 2 fingernails and one toe nail. Which of the following will clinch the diagnosis at the earliest?: (A) Wood's lamp examination, (B) KOH mount, (C) Slit smear (split skin smear), (D) Gram stain
Answer is B. Discolouring and tunneling of the fingernails suggests onychomycosis (Tinea unguium)
Onychomycosis refers to nail infections caused by any fungus, including yeasts and nondermatophyte molds.
KOH mount is used for fungal infections.