Table 5 Features of longitudinal melanonychia compared with those of subungual bleeding-all features are generally true, but there can be individual exceptions
From: Clinical guidelines for the recognition of melanoma of the foot and nail unit
Melanoncyhia | Subungual bleeding |
|---|---|
The duration of history is from 3-6 months upwards to 20 years or more | The duration of history is rarely more than 6 months and is typically shorter |
A history of trauma is quite common | A history of trauma or precipitating activity is quite common |
Lateral margins within the nail are mainly straight and longitudinally oriented | Lateral margins may be irregular |
Where margins merges with the nail fold, pigment may spread onto nail fold (Hutchinson's sign) | Pigment rarely extends from beneath the nail plate |
There are rarely any detectable transverse features | There may be a proximal transverse groove and/or transverse white mark within the nail |
In the absence of clinical tumour, nail plate pigmentation is in continuity with a single zone | Haemorrhage may be broken up into a number of zones |
Dermoscopy reveals | Dermoscopy reveals |
   • continuous pigment between proximal nail fold and distal free edge |    • Pigment may not be continuous in the longitudinal axis, with clear nail at either the proximal or distal margin |
   • in the transverse axis, pigment may vary-whereas in the longitudinal axis it remains largely constant |    • Pigment may vary in any axis |
   • There may be longitudinal flecks of darker pigment within the background pigment of the nail |    • Droplets of blood may be seen separated from the main zone of pigmentation |
   • Pigment is mainly brown black |    • Blood may be seen as a discrete layer of material on the lower aspect of the nail plate at the free margin |
|  |    • Pigment may be purple black, with increasing red hues at margins. It is rarely brown |