What is a dark band within the nail plate extending from the base to the free edge called?

The term for a dark band within the nail plate that extends from the base to the free edge is known as melanonychia. This condition is characterized by an increased production of melanin in the nail matrix, leading to pigmentation that manifests as a dark streak or band. Melanonychia can be caused by various factors, including genetic predisposition, trauma, or certain medical conditions.

Understanding this concept is important, as it can help in differentiating melanonychia from other nail disorders that do not present with the same pigmentation characteristics. Recognizing the appearance and implications of melanonychia can assist in proper diagnosis and treatment if necessary, particularly in distinguishing benign cases from those that may indicate underlying dermatological or systemic conditions.