Employer told I have asperger DISEASE!

Hello, 

I've been off work for 2 months and i recently saw occupational health. Yesterday I received a copy of the report from my initial occupational health appointment which has been sent to my manager. I was really dismayed to read that the nurse had written that I had been diagnosed with Asperger Disease. This has really annoyed me as I did try to explain to the nurse that Aspergers is a part of me and has shaped my personality so the suggestion that that part of me is diseased I find very offensive. I felt I needed to write a letter to occupational health and my manager to explain that its not a disease but my husband said I should let it go as Im wanting occ health to help me but I find it hard to see how telling my manager that I have a disease is helping me.

Would you write a letter to correct their mistake or am I over reacting?