I just got a post from another BD group about a newly-identified autoinflammatory disease called HA20. It has a LOT of symptoms that are just like BD, it usually starts in childhood (and kids have often been misdiagnosed with BD), and it can run in some families. There's actually a gene that you can test for (TNFAIP3) to identify if you or your child has it. There's VERY limited information on it since it was just identified, but here's what I've got so far:
(This web page also has a link to order genetic testing for HA20)
FOR DOCTORS (they'll have full access to these articles):
("HA20: A Novel Autoinflammatory Disease Caused By Haploinsufficiency of A20, Encoded By TNFAIP3")
("Old dog new tricks: Monogenic autoinflammatory disease unleashed")
Hope this helps.