Male cat - dandruff, losing hair above tail, seems painful to the touch.

I was at the shelter for the organization I foster for, and one of the residents, Franklin, has recently been developing a lot of dandruff and losing hair just above his tail. It also seems to be painful because he will growl if you pet or brush him in that area. He's been at the shelter since last fall, and been eating the same food all this time. He doesn't have any fleas, and there are no visible sores, so I'm at a loss as to what it might be. Any ideas?

Thanks!

Hello,

Is he biting, chewing or licking at the area (or any other areas)?  

Has anything in his environment changed?  Has his litter or anything else changed?

Is he otherwise healthy?  Has he been checked for parasites?  Has he had any contact with other cats with health problems?  

I'm trying to help you figure out clues.  Skin conditions can be tricky because so many things can cause them.  He might be in pain.  Maybe a vet visit and blood work are in order.

Good luck!