hypervalinemia and hyperleucine-isoleucinemia (MONDO_0100058, a Monarch Disease Ontology entry) is elevated levels of plasma valine and leucine/isoleucine levels, associated with symptoms of headache and mild memory loss and attributed to biallelic variants in the BCAT2 gene. BCAT2 encodes branched-chain aminotransferase 2 which catalyzes the transamination of the branched chain amino acids to their respective α-keto acids. Also known as: HVLI, branched-chain aminotransferase deficiency, hypervalinemia or hyperleucine-isoleucinemia.