Sounds identical to the case of Marek's we had--it was confirmed by the Dept of Agriculture. You need to know, because if it is, in fact, Mareks you'll need to only have vaccinated birds in your flock from now on. From all I read and studied at the time, I understood that the virus is literally impossible to get out of their environment completely and I have had that confirmed by 2 avian vets and the dept of ag vet who was wonderful about giving of his time and knowledge.
We euthanized our boy-who was about 2 1/2 mo old at the time and absolutely gorgeous. It killed me to do so, but he couldn't live with his legs completely uncontrollable! In our 7-8 years of chickens I have only ever brought in 2 that weren't vaccinated and he was one of them. I even thought about it with an uneasy feeling as I was leaving the hatchery with him (as a replacement for one I had ordered but was unavailable on hatch day). Needless to say, I will never ever do that again!