Childhood
In early childhood, the nail plate is thin and may show temporary koilonychia. Because of
the shape of the matrix, some children show ridges that start laterally by the proximal nail
fold and join at a central point just short of the free margin, to give a ‘herringbone’
arrangement of the ridges (chevron nails). In one study 92% of normal infants aged 8–9
weeks showed a single transverse line (Beau’s line) on the finger nails. One child
demonstrated a transverse depression through the whole nail thickness on all 20 digits.

Old age
Many of the changes seen in old age may occur in younger age groups with impaired
arterial blood supply. Elastic tissue changes diffusely affecting the nail bed epidermis are
often seen historically; these changes may
be due to the effects of ultraviolet (UV) radiation, although it has been stated that the nail
plate is an efficient filter of UVB radiation. The whole subungual area in old age may
show thickening of blood vessel walls with vascular elastic tissue fragmentation. Pertinax
bodies are often seen in the nail plate; they are probably remnants of nuclei of
keratinocytes. Nail growth is inversely proportional to age; related to this slower growth,
corneocytes are larger in old age. Since nails tend to thicken with age and some diseases,
it may well be that the volume of nail production per unit of time does not change.
The nail plate becomes paler, dull and opaque with advancing years and white nails
similar to those seen in cirrhosis, uraemia and hypoalbuminaemia may be seen in normal
individuals. Longitudinal ridging is present to some degree in most people after 50 years
of age and this may give a ‘sausage links’ appearance.