Pointers to nailing a diagnosis

The keratotic papule makes the likely diagnosis an onychopapilloma, a benign tumour of the nail matrix, but in a few cases it might signify Bowen’s disease, a wart or warty dyskeratoma.

A red line on its own without the keratotic papule can be seen in a subungual glomus tumour.

To confirm the diagnosis, lever off the nail and the posterior nail fold and biopsy the exposed matrix.