Please help question regarding daughter

Hello Dr.
My daughter is seven years old and last August I noticed some hypopigmented areas on her knuckles.  She also has a small patch on her wrist and one on her ankles.  Immediately I rushed assuming it was vitiligo.  Three doctors have examined her since then, in October, December and March with a wood;s lamp.  All wood's lamp examinations have been negative.  The spots do not flourensce.  The Dr.'s claim she has pigment, just a lighter shade then her skin.  They showed me an example of lint under the wood's lamp to show me what vitiligo would loook like.  The lint glowed blue-white as oppose to her spots which look a lighter shade of beige than her regular skin.  I asked for a biopsy and the said that the biopsy would show pigmet, therfore a negative vitiligo diagnosis.  
Dr. I wish to believe them, however, I the research I conduct shows the areas of her hypopigmentation to be the exact areas where her marks are.

Can these marks be something other than vitiligo?  Her dx: is post-inflammatory hypopigmentation.  Also, luckily, she is very fair skinned and I apply sunblock daily also locoid cream.  I have seen complete repigmentation on three spots, however, I see two new ones.

Are three wood's lamp examinations within six months enough to rule out vitiligo???

Also, I am concerned as the last examination was done with the light on.  That's were she showed me the difference between the glowing lint and her spots.
Dr. Please help

[Alan Rockoff, MD]

Wood's light examinations should be done with the lights out, to highlight contrast with surrounding skin.  I do not suggest performing a biopsy--and leaving a scar--on a child, since the diagnosis of vitiligo is made on clinical grounds--by looking.  I suggest you wait 3 months and have her looked at again.

Best.

Dr. Rockoff