Homocysteine is a potentially toxic amino acid created in the normal metabolic process of the body. Normally, it is broken down or converted to a non-toxic amino acid. Homocystinurias are a group of genetic conditions in which the level of homocysteine is increased in the blood and urine. According to "Harrison's Principles of Internal Medicine," the most common type affects one in 200,000 newborns.
Homocysteine levels are also increased in a wide variety of conditions, including renal failure, leukemia and inflammatory bowel disease. The inherited diseases lead to severe symptoms that affect many systems in the body. The role of elevated homocysteine in people who do not suffer from these genetic syndromes is less clear.
Neurological and Vascular Symptoms of Homocystinuria
According to "Harrison's Principles of Internal Medicine," the newborn usually appears healthy, though sometimes a low muscle tone is noted. Around age 2, developmental delays become noticeable. Diagnosis is usually made between 3 and 5 years of age.
Homocystinuria may cause mental retardation, psychiatric symptoms and seizures. Vascular disease, formation of blood clots and blocked arteries, which can lead to strokes and heart attacks in children, are also possible. The neurological effects of the stroke depend on the affected location in the brain. The vascular effects are the most severe symptom of these diseases and can lead to death at an early age.
Skeletal and Other Symptoms
According to "Harrison's Principles of Internal Medicine," patients may have a marfanoid appearance, which means they have very elongated limbs and fingers. Dislocated lenses can be one of the first symptoms appearing in the first few years of life. Osteoporosis can also occur. Scoliosis and kyphosis are additional symptoms.
Heart Disease
According to "Harrison's Principles of Internal Medicine," homocysteine increases the formation of clots and contributes to atherosclerosis, which is considered a probable risk factor for heart disease and strokes. A study published in the "Journal of American Medicine" in 1997 concluded that elevated levels of homocysteine greatly increased the risk of heart disease in smokers and people with high blood pressure. A study published in the same journal in 2010 concluded that while there is an association between elevated homocysteine and heart disease, it is not clear that the homocysteine caused the heart disease. Lowering the level of homocysteine did not improve patient outcomes.
References
- "Harrison's Principles of Internal Medicine, 17th edition"; Anthony Fauci et al.; 2008
- "JAMA"; Effects of Homocysteine-Lowering With Folic Acid Plus Vitamin B12 vs Placebo on Mortality and Major Morbidity in Myocardial Infarction Survivors; Jane Armitage et el.; June 2010
- "JAMA"; Plasma Homocysteine as a Risk Factor for Vascular Disease; Ian Graham et al.; June 1997
