HSD10 mitochondrial disease (HSD10MD; OMIM 300438) is a rare X‐linked metabolic disorder caused by pathogenic variants in the HSD17B10 (17‐beta‐hydroxysteroid dehydrogenase X) gene (OMIM 300256) (Zschocke, 2012). The gene discussed is FSIP1; the disease is inborn mitochondrial metabolism disorder.