Black discoloration under toenal

I have been diagnosed previously with a fungal infection under several of my toe nails.  Last year I completed a 90 day regimen of terbinafine.  I went to a dermatologist yesterday who advised me to start another regimen of terbinafine, BUT, there is an area of  black discoloration under the big toenail along with the regular fungal discoloration.  The dermatologist comment waa "this concerns me", I think both because it is a discoloration under the nail and it seems we nave not eradicated the fungal problem.  I probed further, but he thought that it was most likely related to the fungal infection, but he did take digital pictures and scheduled a follow-up in three months. The discoloration has been present for about three or four months and seems to move about the nail slightly over time, but does not seem to "grow-out"  It is not a streak and does not originate from the matrix, but is on the proximal edge of the infected area of the nail in the center and left quadrant of the nail (but outside of the lunina area).  The area is irregular in size, with the largest dimension being about 5 mm.

From what I have read, melanoma of the toenail is rare, but can be nasty stuff.  I am a relatively healthy male caucasion, 48 years old.  What can you tell me about melanoma under the toenail, and should I be really concerned?  Three months seems like a long time to wait.  Also, I have read that most melanomas originate in the matrix. This does not.  Good news?

As you can tell, I am concerned.  Thanks for your help...

[Alan Rockoff, MD]

I think your dermatologist is approaching things the right way.  First, blood under the great toenail from trauma is a lot more common than melanoma.  Second, you say the pigment doesn't start at the matrix and is growing out slowly.  Third, the only way to test for melanoma is to do a biopsy, and needless to say that is a traumatic affair, because you have to take a piece of skin from under the nail.  So it's a reasonable approach to photo and wait.  Nails grow slowly.

By the way, discoloration of the big toenail is often from the trauma of everyday life and not fungal--given that it survived a course of Lamisil, that may well be the case with your nail.

Take care.

Dr. Rockoff