As usual, the list does not contain Porphyria. Well, maybe Porphyria is so rare that only a very small percentage of people will be represented in the group tested. But for those few, lack of diagnosis can mean a lifetime of misery, and not only for themselves, but everyone who loves them or depends on them.

As a person dx'd with both, as my friends here know, I am never absolutely sure if I have MS caused by Porphyria. But my reply to that is this: doctors do not even agree on what causes MS. It could be a chemical cause, as has been stated on this forum in the past; thus, it could be caused by excess porphyrins, which are a precursor to heme.
This list is a good pointer to what should be considered, but it does not really address what is the cause of MS and how it may differ--or be a part of--the listed conditions.
After all these years, we do not have a clear vision of what causes MS. This is certainly the opinion of the MD's I have gone to. No wonder they have trouble diagnosing!
MS probably has more than one root cause. Swank saw one of them; others see others of them.
But just wanted to add this again, as before: Porphyria is ALWAYS left off the list. And it should be on the list for the differential diagnosis.