Undeveloped or Deformed Chest Cavity

One of the chicks from my most recent hatch had an underdeveloped or deformed chest cavity.
This is what I observed.....
For the first two days I could tell something was wrong with the chick, but couldn't put my finger on it. It wasn't stargazing/wryneck or splay leg, but the chick was completely off balance and just looked odd. It was also carrying its wings very strange. It was also doing a lot of open mouth breathing, but no goo or watery eyes like you would see with a respiratory illness. It also hatched out that way.
Just to be safe, I kept it seperate under a brooder lamp to see if it would perk up. The poor thing just started just falling over forward, and just seemed to be getting worse. As I was holding it I noticed its chest felt strange. It was very flat. I went and compared it to one of the healthy chicks and sure enough its chest cavity felt and looked totally different. It also looked more like a penguin chick than a chicken when it was standing. It was really weird.

I did decide to cull, that seemed to be the most humane thing to do

Has anyone else ever had this happen?

~Steph