went to see a derm.. confused?

[rob1]

I was just about to start taking generic propecia and decided to see a derm. I have been thinning on the top of my head for about a year, I then noticed I had 3 small bald patches (about an inch wide) in different places on the top. The patches were very red and burned alittle. The derm said he did not think these patches were from male pattern baldness. He gave me some olux foam and told me to use it 2 times a day and come back in 4 weeks. He said if he did not see any new growth he wanted to do a biopsy of the scalp. Has anyone ever heard of this, he said he would cut a small piece of scalp and send it to the lab. What kind of things would he hope to find? I asked him but he really did not give me an answer. I was wondering what could make these bald patches if it was not from male pattern baldness. Any help or advise would be very helpfull, thanks