Which statement is true about onychomycosis?

• A. It is caused by fungus
• B. It is caused by bacteria
• C. It never affects toenails
• D. It cannot be treated

Answer: (A)

Onychomycosis is a fungal infection of the nails. Fungi, typically dermatophytes, invade the nail plate and bed, causing changes such as discoloration, thickening, and separation from the nail bed. Because it is caused by fungus, the statement that it is caused by fungus is the correct one. It is not caused by bacteria, so attributing it to bacteria is inaccurate. It commonly affects toenails, so claiming it never affects toenails is false. It can be treated with antifungal therapies, so saying it cannot be treated is incorrect; treatments include topical or oral antifungals and sometimes nail removal to manage the infection.