Probably from the various bioweapon-related vaccines like the Anthrax vaccine among others.
Us military isn't exactly known for limiting soldiers exposure to awful chemicals. Seems like all my vet friends and family members have some kind of malady caused by exposure to random toxins.
Guillain–Barré syndrome[0] is a rare reaction to vaccination that causes the body to attack its own nerves and damage the myelin sheath. Possibly related?