Concave nail SNOMEDCT_US:66270006 HP:0001815 UMLS:C0221261 Koilonychia HP:0001598 Koilonychia literally means spoon nails. This often results in a saucer- or spoon-shaped nail and the free edge of the nail is typically everted. The affected digits should be specified. Note that the bundled term koilonychia is an abnormal shape of the fingernail where the nail has raised ridges and is thin and concave. Spoon-shaped nails The natural longitudinal (posterodistal) convex arch is not present or is inverted. Nail dysplasia