What is homocysteine?
Homocysteine is an amino acid that is produced from another amino acid, methionine. Normally, homocysteine is then converted into the amino acids cystathionine and cysteine. In homocystinuria (HCU) the process is faulty and thus high homocysteine levels are generated. A buildup of homocysteine in plasma, tissues and urine promotes the clinical manifestations of the disease and is a hallmark of HCU.