Onychophosis is a localized or diffuse hyperkeratotic tissue that develops on the lateral or proximal nailfolds, within the space between the nailfolds and the nail plate, and is a common finding in the elderly. Onychophosis may involve the subungual area, as a direct result of repeated minor trauma, and most frequently affects the first and fifth toe.^[1]

• Cohen, Philip R.; Scher, Richard K. (1992). "Geriatric nail disorders: Diagnosis and treatment". Journal of the American Academy of Dermatology. 26 (4). Elsevier BV: 521–531. doi:10.1016/0190-9622(92)70075-q. ISSN 0190-9622. PMID 1597537.
• Cox, Kasey; Mervak, Julie E. (2023). "Nail plate split of the fifth toenail". JAAD Case Reports. 39. Elsevier BV: 55–57. doi:10.1016/j.jdcr.2023.06.046. ISSN 2352-5126. PMC 10424070. PMID 37583836.

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