Having vertical (longitudinal) ridges on the fingernails refers to the presence of tiny raised lines or ridges that run up and down the length of the nail. Ridges are among the different kinds of nail abnormalities that can develop due to aging, trauma, or underlying medical conditions. Many people notice an increase in vertical ridges of the fingernails as they age, and this can be a normal development. Aging has been described as the predominant cause of vertical ridges on the fingernails. Onychorrhexis is the medical term used to describe longitudinal ridges on the nails that often accompany brittle nails.

In contrast to longitudinal ridges, Beau's lines are horizontal or transverse depressions in the nail that may be confused with nail ridging. These are caused by diseases that affect the entire body, including malnutrition, heart attack (myocardial infarction), severe infections, and metabolic disturbances, including poorly controlled diabetes.

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