Not CMT but still no diagnosis

My father in law has a condition which looks very similar to Charcot Marie Tooth (hands stuck in claw like grip, requires braces to walk), however he's gone through every test to determine the cause to no avail. Earlier on in the disease he was diagnosed with ALS, but he would have died a long time ago.  He's 78 and had the first onset of symptoms in his early 40's (started with muscle twitches).  

He's very healthy other than diabetes which he controls through diet (diabetes came after the onset of symptoms), and some heart problems which are under control with Coumadin. He's gone through a lot of tests and he's pretty much given up on figuring this out. Privately, he thinks it might have something to do with the severe appendicitis he had when in his late 30's (he almost died). Other than that there is no known history of this kind of condition in the family.

My wife occasionally has muscle twitches which has her worried she might have the same problem.  Since her father has given up on a diagnosis we're trying to rule out a genetic link.