Homocysteine (Elevated Homocysteine, Homocystinuria, Hyperhomocysteinemia)

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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What is homocysteine?

Homocysteine is an amino acid that is produced by the body by chemically altering adenosine. Amino acids are naturally made products, which are the building blocks of all the proteins in the body.

Can elevated homocysteine levels be genetic?

In 1969, Dr. Kilmer S. McCully reported that children born with a genetic disorder called homocystinuria, which causes the homocysteine levels to be very high, sometimes died at a very young age with advanced atherosclerosis in their arteries. Homocysteine levels in the blood may be elevated for many reasons. More specifically, these reasons can be divided into severe genetic causes and other milder causes.

In the genetic condition called homocystinuria, there is a deficiency or lack of an important mediator molecule (enzymes) in the complicated homocysteine breakdown pathway. This leads to severely elevated levels of homocysteine. In this rare and serious condition, there is a constellation of symptoms that include developmental delay, osteoporosis (thin bones), visual abnormalities, formation of blood clots, and advanced atherosclerosis (narrowing and hardening of blood vessels). This condition is mainly recognized in childhood.

Milder genetic variations are more common causes of elevated homocysteine levels (hyperhomocysteinemia). In these conditions, the mediator molecules malfunction and are less efficient because of minor abnormality in their structure. They also lead to elevation of homocysteine levels, although much milder than in homocystinuria, by slowing down the breakdown of homocysteine.

Medically Reviewed by a Doctor on 11/11/2015

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