For me, the key insight here is that the five genes now known to be associated with familial ALS are all fairly disparate. That suggests that ALS is ultimately multiple diseases, although there is a final common pathway producing symptoms that are largely indistinguishable from each other. (Some specific genetic mutations are admittedly associated with faster progression).
My strong feeling is that this paradigm actually applies to a lot of different diseases. From a drug development standpoint, if you intervene at a late enough stage you may not care what the actual driver is. But intervening at a late stage pathway is very likely to be inferior to intervening nearer the root cause of the disease. But intervening at an early stage without being able to identify which patients you should be treating is also going to cause problems - some patients in your trial simply won't respond.
Peter
(This is a copy of a post I made on SI - figured it would be of interest here too)
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