HSD17B10 and HSD10 mitochondrial disease: With the finding that a silent mutation in HSD17B10 (previously denoted HADH2) [16] was associated with normal isoleucine metabolism in a family with nonprogressive, syndromic form of X-linked mental retardation (MRXS10) (OMIM#300220), the possibility of other disease mechanisms was suggested [2], [17].