Which statement about onychomycosis diagnosis is true?

• A. Onychomycosis is diagnosed clinically
• B. Cultures are always required
• C. Diagnosis requires a biopsy
• D. Diagnosis cannot be made without imaging

Answer: (A)

Onychomycosis can often be identified based on how the nail looks and behaves. The characteristic pattern—thickened, deformed nails with subungual debris, yellow or white discoloration, and possible onycholysis—fits the classic clinical picture enough that a clinician can make a working diagnosis without invasive tests. That’s why diagnosing it clinically is considered true and practical in many cases.

Lab tests, like a potassium hydroxide prep or fungal culture (or histopathology with PAS), are commonly used to confirm the diagnosis or to identify the specific organism, especially when the presentation is unclear or treatment decisions depend on the organism. However, these tests are not strictly required for every case to call the diagnosis.

Biopsy is not routinely required for straightforward cases, as it’s invasive and reserved for atypical presentations or when malignancy or other nail diseases are suspected. Imaging isn’t used to diagnose onychomycosis either; it has no role in establishing the fungal infection itself, though it may be relevant if there are concerns about underlying bone involvement in severe cases.

So, recognizing the nail changes clinically provides the true basis for diagnosis in many scenarios, with lab tests used to confirm or refine as needed.