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.
