Diagnosis using the proximal and lateral nail folds.

This article includes the etiology and pathophysiological data of each entity, classifying them as dermatologic, systemic, infectious, neoplastic, traumatic, and other classifications. The entities inherent to the periungual folds are also included, such as acute paronychia, chronic paronychia, retronychia, hangnails, hematomas of the proximal fold caused by oximeter, onychocryptosis, hypertrophy of the lateral folds, and infections caused by Candida albicans, Pseudomonas, and Staphylococcus aureus. Additionally, pathologies caused by diabetes mellitus, sepsis, endocarditis, drug reactions, and finally less frequent diseases that also affect the nail folds are discussed.