My ds is a neuromuscular condition called hereditary spastic paraplegia. His gene fault is one of the rarest (estimated 1 in a million people).
It’s a form of upper motor neuron disease. Basically the nerves in his spine are degenerating so the messages get mixed up and he’s lost feeling in half of one leg, his muscles are wasting and he has spasticity.
Luckily it isn’t life threatening.
Sorry to hear your DH has a degenerative condition too. It’s hard knowing it’ll get worse and how but not any timescales of speed.