This document provides a review of nail abnormalities associated with systemic diseases. It begins by classifying nail abnormalities into four categories: 1) nail abnormalities less specifically associated with systemic disease, 2) nail abnormalities more specifically associated with systemic disease, 3) nail abnormalities associated with disease of a specific organ system, and 4) nail abnormalities associated with specific syndromes or genodermatoses. Within these categories, the document describes various nail changes and abnormalities and the systemic diseases they may indicate, such as splinter hemorrhages indicating subacute bacterial endocarditis, Muehrcke's lines indicating hypoalbuminemia, and clubbing indicating cardiopulmonary disease.