Why is my zebra danio crooked?

[Snuffleupagus]

I've had this fish for a few weeks, and it seems to be doing as well as the other zebras, but it looks funny (and has since I got it). It also seems like it has to swim harder to keep up with the others, because of its relatively small tail. How on earth did it end up all crooked and with a tiny tail?

 

[Zagz]

Could be a birth defect. I had a serpae tetra that swam with his mouth towards the top of the tank all the time, he was fine otherwise.

 

[talloulou]

Could also be fish tuberculosis.

 

[Todd2]

I had a zebra danio that had a "crook" in its body. I think it was a birth defect because it had always been there. None the less it was happy and kept up with the other danios.