Abstract
There are some important points to note
concerning the examination of abnormal nails
for colour changes. The nails should be studied
with the fingers completely relaxed and not
pressed against any surface. Failure to do this
alters the haemodynamics of the nail and
changes its appearance. The finger tips should
then be blanched by pressing them on an even
surface to see if the nail bed is grossly altered;
this may help to differentiate between discoloration of the nail plate and its vascular bed. If
the discoloration is in the vascular bed, it will
usually disappear. Further information can be
gleaned by transillumination (diaphanoscopy)
of the nail using a pen torch placed against the
pulp. If the discoloration is in the matrix or soft
tissue, the exact position can be identified
more easily and dark material or a non-transparent foreign body will give a dark shadow.
Furthermore, if a topical agent or superficial
infection is suspected as the cause, one can
remove the discoloration by scraping or cleaning the nail plate with a solvent such as
acetone. If the substance is impregnated more
deeply into the nail or subungually, microscopic studies of potassium hydroxide preparations, tangential or punch biopsy specimens
using special stains may be indicated. Wood’s
lamp examination is sometimes useful.