What are visible depressions running across the width of the natural nail plate due to major illness called?

Visible depressions running across the width of the natural nail plate that occur as a result of major illness are referred to as Beau's nails. This condition is characterized by transverse grooves or indentations that form during periods of illness, trauma, or severe stress, reflecting temporary disruption in nail growth.

Beau's lines can emerge due to various health issues, such as systemic diseases, infections, or nutritional deficiencies that affect the body’s ability to sustain normal nail production. The presence of these lines serves as a historical marker of past health events that affected the individual, indicating periods where the nail matrix was compromised, leading to the formation of grooves instead of smooth, uniform nail growth.

Other conditions mentioned, such as hangnails or fungus, refer to different nail problems that do not present with the specific pattern associated with Beau's nails, and eggshell nails indicate a different malformation characterized by thin, fragile nails. Understanding the unique features of each condition helps in correctly identifying nail disorders based on their characteristics.