So my second forgotten beast was a skinless skink with a pair of antennae. It also had a deadly dust attack. The FB died pretty easily, but not before filling the tunnels with dust.
After a few minutes the militia who fought it began to go blind and paralyzed. They suffocated to death and I lost five of them just like that. I knew stuff like that happened, so I rebuilt my militia and moved on.
Soon after the FB's death random dwarves were catching bouts of fever, numbness, and partial paralysis. I was fine with that too since none of them died.
And then after a goblin ambush on the surface one year later I started to get suffocation notices. Mostly dogs, cats, and children. Somehow the inhabitants of the fort were getting the FB extract, which was quiet for a year, on them. I think it has to do with how coverings can transfer all over the place. Only one adult died from the second wave, and she was less than twenty years old anyway.
Anyone else encounter stuff like this? I'm fairly sure it is caused by forgotten beast extract since I've seen it on the affected animals. The dwarf who died in the second wave was hauling the body of a cat who had suffocated, so is it possible that syndromes are transmissible. Generally the older dwarves seem resistant; they get sick but don't croak. And the doctors don't seem interested in dealing with it, assuming they can deal with it at all.