Monarch Disease Ontology id MONDO_0018323 (HSD10 disease, neonatal type) is the most severe form of HSD10 disease, a rare neurometabolic disorder. It is characterized by onset of severe metabolic/lactic acidosis, neurological and psychomotor delay, seizures and severe progressive hypertrophic cardiomyopathy in the neonatal period. Hepatic involvement and coagulopathy are rare. The disease is fatal within the first months of life. Also known as: 2-methyl-3-hydroxybutyric aciduria, neonatal type, 2-methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency, neonatal type, HSD10 deficiency, neonatal type, MHBD deficiency, neonatal type.