I was diagnosed with mono a couple days before taking the subject GRE, and obviously didn't do so well. I ended up not mentioning it in my personal statement, because I decided to focus on the positives (and really wanted to talk about the research and experience I have outside the classroom, since I definitely wasn't going to get in on the strength of my GPA/GRE alone.) So far I've been accepted to a couple programs, so I don't regret my decision at all. However, if I hadn't gotten in, I might have regretted it--what if that would have been the difference between a rejection and not?
Maybe talk to your recommenders, and see what they suggest. My academic director suggested that I have a prof who knows my work comment on it in the LOR, since they'd have more authority to say that they thought I could do better than I did (obviously, any student has excuses for why they didn't do better.)