Hi Jeanie, welcome.
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TAM is a very rare, very variable disease but there are quite a number with it worldwide. A good physiotherapist may help, particularly a neurophysio, although TAM is not neurological.
There will be something that will help your brother, the difficulty is finding it. Just a word of warning, TAM attacks the muscle's ability to recover from exercise, so gritting your teeth and continuing to exercise despite muscle pain can do a lot of damage and progress the disease.
Good luck.