Trying to identify leaf disease
 

Have had Acer Brilliantissmum for 5yrs, every year it starts to leaf, and within a short while leafs start to form red blotches, with raised lumps. As the season goes on these merge across the whole leaf. I can not find this problem listed in any books I have, any help would be gratefully recieved.
Tried to upload a picture, but upload kept failing, any help on that would be good as well.

Thanks Ron