Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (mHS) deficiency is an autosomal recessive inborn error of metabolism, which will give rise to failure of ketogenesis in liver during illness or fasting. It is a very rare disease with only a few patients reported worldwide, most of which had a good prognosis after proper therapies. | Severe clinical manifestation of mitochondrial 3-hydroxy-3-methylglutarylCoA synthase deficiency associated with two novel mutations: A case report