There is no specific exception for a disabled non-dependent.
But, he/she may qualify under the "medical dependent" exception:
If your close relative cannot be your dependent because he had more than $4,300 of gross income, but otherwise would have qualified as your dependent (basically that you & other family members provided more than half his support), then you can include in your deductible medical expenses (on Schedule A) any qualifying medical expenses you paid on his/her behalf just as if he/she was your dependent.
