Pregnancy‐associated acquired arteriovenous malformation of the nail unit: a novel cause of localized erythronychia

Localized longitudinal erythronychia describes a solitary red streak limited to a single nail unit. Localized longitudinal erythronychia can be caused by both benign and malignant entities. Most commonly, the cause is a benign process, such as an onychopapilloma. We report a case of an acquired subungual arteriovenous malformation that presented as localized longitudinal erythronychia during pregnancy. To our knowledge, this is the first report of localized longitudinal erythronychia arising from a pregnancy‐associated arteriovenous malformation of the nail unit.