Homocysteinemia is a medical condition that occurs when there are high levels of the amino acid homocysteine in the blood. This condition has been linked to cardiovascular disease and other health problems. The term homocysteinemia can be broken down into two parts: homo - means "same" or "equal"; cystein - refers to the amino acid cysteine. Synonyms for homocysteinemia, include hyperhomocysteinemia, homocystinuria, and cystathionine beta-synthase deficiency. Hyperhomocysteinemia is used to describe a high level of homocysteine in the blood, while homocystinuria and cystathionine beta-synthase deficiency are genetic disorders that can cause high levels of homocysteine in the body.