I have a four year old girl in good health. She has been potty trained for quite a while. At first, when she was switching from diapers to 'big girl panties' she had accidents (usually when away from home). Then they stopped. Then all of a sudden she started peeing on the floor. At first we thought it was an accident - she'd wait too long to go, or someone would be in the bathroom. Then she climbed into a tent full of stuffed animals and peed all over them. We didn't make a big deal - we cleaned the animals, took away the tent. Then we started finding pee spots in her room, and even finding pee in her toys! She took poop in a bucket, and in one of her toy containers. She started going pee on her floor, even when no one was in the bathroom. She decided she wouldn't have to go bed if her bed was wet, and peed on it. She got mad at her dad, and peed all over her toys on her floor. Just today, she opened the trunk of a 'car' she has and peed in it - this is one of her favorite toys, and she plays with it daily.
She's very intelligent. She knows her entire alaphbet - she can recognize individual letters. She knows all her colors. She can count to 20 (English), 8 (Spanish), and knows some Chinese numbers/words. She can even count backwards (from at least 8) in English. She has never been a formal classroom or preschool. She has learned to manipulate the members of the house to get what she wants. Rewards don't work with her - she will flat out tell you she doesn't want it or doesn't want to go instead of readily doing what it is you want her to do. She screams at nap/bed time. Often she refuses to pick up her toys.
We are slowly working on her anger/screaming/attitude when she is asked to do something by an adult - and she is showing signs of impovement. But I do not know what to do about her refusing to use the potty. I know that offering a reward for going on the potty would be abused by her, and when removed would likely cause her to go back to peeing in anger.