The 17-Beta-Hydroxysteroid Dehydrogenase X gene (HSD17B10/HADH2 OMIM 300256), codes for the hydroxysteroid (17β) dehydrogenase 10 protein which catalyzes the oxidation of steroid modulators, hormones, and xenobiotics (Yang, SY et al. PNAS 2009; 106(35):14820-14824). Alterations of HSD17B10 blocks the isoleucine degradation pathway and lead to metabolic disease (Fukao, T. et al. Mol Genet Metab 2001;72:109-114). The HSD17B10, located at Xp11.2, contains 6 exons. Mutations in HSD17B10 are associated with X-linked recessive mental retardation syndrome characterized by choreoathetoid movements, hypotonia, behavioral abnormalities, and mild mental retardation (Reyniers, E. Am J Hum Genet 1999;65:1406-1412).