Localized longitudinal erythronychia: diagnostic significance and physical explanation.

BACKGROUND Longitudinal erythronychia (LE) is a term for red streaks in the nail. We describe the range of diseases manifested by localized (single or bifid) LE and explain the underlying physical changes. OBSERVATIONS Longitudinal erythronychia can be multiple or localized. Multiple lesions typically indicate an inflammatory disease such as lichen planus. When localized, they may be a single or bifid streak arising through a benign or malignant neoplasm, scarring of the dermis or epidermis, or the first stage of an inflammatory process that may evolve into multiple LE. Excision of a localized LE may provide a diagnosis and cure. Incisional matrix biopsy of multiple LE may provide a diagnosis. Clinical manifestation of LE arises through reduced compression of the nail bed due to loss of bulk of the nail plate with a groove on the undersurface. A streak of thinned nail then allows an enhanced view of a corresponding streak of engorged nail bed. The reduction in nail thickness renders it more fragile with a tendency to split distally. CONCLUSIONS Understanding LE can assist in diagnosis and explanation to the patient. Localized LE may represent a focal tumor or dysplastic process.