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Longitudinal Erythronychia — SCE Dermatology MCQ

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HardNail DisordersLongitudinal ErythronychiaSCE Dermatology

A 50-year-old woman has nail changes showing a longitudinal red line (erythronychia) in a single fingernail. The line extends from the proximal nail fold to the distal edge with a small area of distal fissuring. What differential diagnosis should be considered?

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Correct answer: B — Onychopapilloma, glomus tumour, Bowen disease or melanoma requiring nail-unit assessment

The best answer is “Onychopapilloma, glomus tumour, Bowen disease or melanoma requiring nail-unit assessment”. Nail findings localise disease to matrix, bed or periungual tissue; a new changing longitudinal pigmented or erythronychic band requires specialist assessment because benign and malignant causes overlap. The alternatives “Longitudinal ridging from age-related matrix change, when the full phenotype supports it”, “Diffuse nail-bed erythema from chronic liver disease, within an appropriate UK pathway”, “Transverse erythronychia after systemic illness, after clinicopathological correlation”, “Distal onycholysis from irritant hand dermatitis, after specialist assessment” are clinically adjacent possibilities, but they do not fit the defining morphology, distribution, histopathology, risk signal or management sequence in this stem.

Reference: DermNet specialist nail terminology reference: https://dermnetnz.org/topics/nail-terminology