Could it be leaf gall?

This is similar to a problem I'm having with my camelias which I've been posting about this week. I just noticed today that the underside has turned white. And it's affecting a small amount of leaves.

i think dorie is correct. i have seen it on my camellias before but not as often as on the azaleas. it is not the same fungus, however, that attacks both plants, and can be controlled with fungicides. i usually hand-pick the galls and throw them in the garbage, not on the surrounding soil. they can mature and produce spores if you leave them in the area.

Attached is just one link which discusses leaf gall of Camellia. It is quite common in some years. Your good 'housekeeping' (IPM) practices now will reduce the chances of another infection next year.

Here is a link that might be useful: Camellia leaf gall

Good news is it not serious and won't kill the plant....but it sure is ugly.