Fungus A type of microorganism that can grow on and infect nails, causing discoloration, thickening, and other symptoms.Related Articles: Nail Dust Hazards: Perfect Nails but at What Cost?Dust - when filing, shaping and painting hundreds of nails a week is an occupational hazard.Glossary: Fungal infectionThe Bed Epithelium TissueNail Conditions (Part 1)The Fungal Nail