Subungual Nail Erythrasma Presenting as Melanonychia: A Rare Finding

Jalal Maghfour; Jennifer Kane; Leslie Robinson-Bostom; John Kawaoka; Nathaniel Jellinek

doi:10.1159/000510674

Subungual Nail Erythrasma Presenting as Melanonychia: A Rare Finding

Skin Appendage Disord. 2021 Jan;7(1):41-45. doi: 10.1159/000510674. Epub 2020 Oct 5.

Authors

Jalal Maghfour¹, Jennifer Kane², Leslie Robinson-Bostom², John Kawaoka², Nathaniel Jellinek²

Affiliations

¹ Tulane Medical School, Tulane University, New Orleans, Louisiana, USA.
² Dermatology, Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA.

Abstract

Nail pathology may reflect a wide array of localized and systemic dermatological conditions. Certain nail findings such as melanonychia can create diagnostic challenges even to nail experts. We report a case of a 78-year-old man who presented with melanonychia of the great toe. Nail clipping showed focal melanin deposition, and dermoscopy demonstrated a region of localized erythema in the lunula concerning for possible melanocytic neoplasm. Subsequent nail biopsy showed numerous vertically oriented filamentous bacteria and coccobacilli within the nail plate consistent with a diagnosis of subungual nail erythrasma. Nail erythrasma is a rare entity. Additionally, this case highlights a new clinical presentation of nail erythrasma as melanonychia.

Keywords: Cornyebacteria; Erythrasma; Nail matrix; Nail plate.

Publication types

Case Reports