Problem is a lot of the late onset don't even know they have the disease much less are seeing a genetist. I think I saw an episode on Mystery Diagnosis once with Fabry patient. Was diagnossed in 30's or 40's had noticed some signs early in life (lack of sweat) forget what but probably not till kidney problems got more troublesome and then from doc to doc.
jq can respond better than I but there are several things to keep in mind about the switches. They aren't exactly enrolling hundreds of patients. Patients stop any therapy (even ERT) for many reasons with ERT could be AE's or costs (you often get free care in trials and even if ERT paid for could have other costs/copays)
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