What is the term for a contusion caused by an injury or disease of the nail unit?

The term that refers to a contusion caused by an injury or disease of the nail unit is a nail disorder. Nail disorders encompass a wide range of conditions that can affect the structure, appearance, and function of the nails. A contusion, specifically, is a type of bruise that occurs when the small blood vessels under the nail are damaged, leading to discoloration. This phenomenon is categorized under nail disorders because it reflects an abnormal condition related to the nail unit's integrity, whether due to trauma or underlying health issues.

Other choices like eggshell nails pertain to a specific condition characterized by thin, weak nails, whereas the nail plate refers to the hard part of the nail that is visible and protects the underlying tissues. The nail fold describes the skin at the edges of the nail plate but does not define a condition or disorder. Understanding these definitions helps in distinguishing between various nail-related issues efficiently.