Re-applying to the PhD Program after Illness
I'll slightly replicate my answer to this question: mention this, but don't be too melodramatic. You have dealt with an illness that was out of your hands and got a handle on it. This is not something that a reasonable admissions committee will see as a point against you, but be sure that they understand you are not looking to get accepted because of your illness. It is also might be illegal to discriminate against you because of illness, depending on its nature and the country you're in. 

Good luck!