THE MOST COMMON NAIL DISEASE: TOENAIL FUNGUS By Bethesda, MD & Springfield, VA Podiatrist, Dr. Paul Ross What Is Toenail Fungus? Toenail fungus, also known as onychomycosis or tinea unguium, is a fungal infection that affects the nails. It may begin as a discoloration on the tip of the nail, usually yellow, and nails eventually…