Definition: Thicken toenail resulting from the invasion of the toenail by different fungal elements.

Fungus is an opportunistic organism due to several factors, including trauma, aging, decreased blood flow, circulatory disorders, smoking, diabetes, and other situations that would cause a decrease in the immediate blood flow to the area. The fungus is able to penetrate the toenail and begin to cause thickening and discoloration. End results often include highly incurvated toenails with pain and discomfort from pressure or chronic infected ingrown toenails.

Therapy often includes topical applications to get ride of fungus. Other more radical forms of therapy include oral medications and/or surgical removal of part or the entire toenail.