If covered by polish, clean them first with a solvent like acetone. Then pay attention to color and shape but
also to anatomic details :
Lunula: The white half-moon at the proximal edge of the nail bed
Cuticle: The thin skin adherent to the nail at its proximal portion
Perionychium: The epidermis forming the ungual wall at the sides and back of the nail
Although fingernails tend to be more informative than toenails (since they grow more rapidly and suffer
fewer traumas), always examine them both. Inspect them first without applying any pressure. Then, blanch
the fingertip to see if a pigmented lesion changes color (which would argue for discoloration of the vascular
bed rather than the nail plate). Finally, place a penlight against the finger pulp and shine it through the nail. If upon illumination a discoloration disappears, it is also more likely to be in the vascular bed than in the soft
tissue or matrix. When indicated, scrape the nail plate surface, and do a potassium hydroxide preparation to
rule out fungal disease. Note that nail changes due to systemic disease (as opposed to trauma) often occur in the matrix, so that the leading edge of the abnormality (for example, a pigmentation change) is usually shaped like the distal portion of the matrix. To estimate the time of initial insult, measure the distance from the proximal nail fold (cuticle) to the leading edge of the pigmentation change, remembering that nails grow
0.1–0.15 mm/day.
also to anatomic details :
Lunula: The white half-moon at the proximal edge of the nail bed
Cuticle: The thin skin adherent to the nail at its proximal portion
Perionychium: The epidermis forming the ungual wall at the sides and back of the nail
Although fingernails tend to be more informative than toenails (since they grow more rapidly and suffer
fewer traumas), always examine them both. Inspect them first without applying any pressure. Then, blanch
the fingertip to see if a pigmented lesion changes color (which would argue for discoloration of the vascular
bed rather than the nail plate). Finally, place a penlight against the finger pulp and shine it through the nail. If upon illumination a discoloration disappears, it is also more likely to be in the vascular bed than in the soft
tissue or matrix. When indicated, scrape the nail plate surface, and do a potassium hydroxide preparation to
rule out fungal disease. Note that nail changes due to systemic disease (as opposed to trauma) often occur in the matrix, so that the leading edge of the abnormality (for example, a pigmentation change) is usually shaped like the distal portion of the matrix. To estimate the time of initial insult, measure the distance from the proximal nail fold (cuticle) to the leading edge of the pigmentation change, remembering that nails grow
0.1–0.15 mm/day.