What condition is characterized by nail thickening and discoloration?

Onychomycosis is a fungal infection of the nails, which leads to observable symptoms such as nail thickening and discoloration. The condition results from the invasion of various fungi, affecting the nail bed and the structure of the nail itself. As the infection progresses, the affected nails become brittle, discolored, and can produce a foul odor. The thickening often occurs as the body attempts to combat the infection, leading to an altered nail appearance.

In contrast, psoriasis is an autoimmune disorder that can affect the nails but typically presents with pitting, ridges, and discoloration, rather than the characteristic thickening associated with onychomycosis. Beau's lines are indented ridges that run across the nail and are indicative of a temporary interruption in nail growth, often caused by factors such as illness or trauma, which does not include thickening. Leuconychia refers to white spots or discoloration on the nails, commonly caused by minor trauma or underlying health issues, but it does not involve the thickening of the nails. Therefore, onychomycosis is the condition most commonly associated with both thickening and discoloration of the nails.