3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) Lyase Deficiency is a rare autosomal recessive disorder, with most individuals diagnosed coming from Saudi Arabia, Portugal, or Spain. Mutations found in the HMGCL gene can cause (HMG-CoA) lyase deficiency. HMG-CoA lyase plays an important role in breaking down dietary proteins, specifically the processing of the amino acid leucine. and the production of ketones during fat metabolism. Signs and symptoms of HMG-CoA lyase deficiency usually appear within the first year of life and can include vomiting, diarrhea, dehydration, extreme tiredness (lethargy), weak muscle tone (hypotonia), hypoglycemia and metabolic acidosis.