Amanda Truth Project

http://thejns.org/doi/full/10.3171/2009.1.FOCUS08302?cookieSet=1

Conclusion of the study is that "Moyamoya disease is an important cause of stroke in children and young adults."

Hereditary is not a word normally used with Moyamoya; however, in this study the authors conclude:

"To date, reports on familial moyamoya have been limited to Asian families. Given considerable evidence of differing genetic susceptibility between Asian and North American populations,16,73,75 future studies are needed to clarify inheritance patterns in North American pedigrees of familial moyamoya and to replicate linkage analyses within these patients."

My daughter was part Japanese.  I don't think the hospital staff ever realized that.  And given that this study was out in April 2009 they might not have known any of this information yet.