FSIP1 and HSD10 mitochondrial disease: In addition, elevated excretion of urinary 2M3HB and TIG indicates not only BKTD but also HSD10 mitochondrial disease (HSD10MD, OMIM #300438), which is a rare X-linked recessive disorder caused by a hemizygous or heterozygous mutation in the HSD17B10 gene [20].