About homocysteine

About homocysteine

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.


What are the risks of elevated Homocysteine levels?

The risk of having cardiovascular issues, skeletal abnormalities, ocular issues, and cognitive impairment rises when homocysteine levels rise above normal.

Normal versus concerning blood levels of homocysteine

What is Homocystinuria (HCU)?

Homocystinuria is a disease in which an enzyme called cystathionine beta synthase (CBS) is not working properly leading to very high levels of homocysteine and low levels of cysteine. If untreated, there is a very high risk of thrombotic events such as strokes and heart attacks, ocular issues including myopia and lens dislocation, skeletal issues such as scoliosis, and cognitive issues such as executive functioning deficits, and even severe mental retardation.

More about HCU

What are the risk factors of homocystinuria?

HCU is a genetic disease, so if one of your family members has been diagnosed with HCU, you have a higher risk of having the disease. The disease itself is also highly varied in its presentation and the age at which symptoms appear. Patients can have mild, moderate, or severe disease and different patients can have different body systems affected. Some common symptoms include:

  • VASCULAR SYSTEM: Strokes, heart attacks, embolisms
  • SKELETAL SYSTEM: Osteoporosis, fractures, scoliosis, long limbs
  • CENTRAL NERVOUS SYSTEM (CNS): Attention deficit, developmental delay, depression, intellectual disability
  • OCULAR: Myopia, Ectopia lentis (lens dislocation)

Sometimes HCU is mistaken for Ehlers Danlos syndrome or Marfan syndrome.

“Patients living with homocystinuria today suffer from severe side effects of the ophthalmic, skeletal, cardiovascular and neurocognitive systems yet there are no effective treatments for this disease.”
— Denaé Barker

How is HCU diagnosed?

Homocystinuria is diagnosed by a blood test. Patients with HCU will often have high methionine and homocysteine levels in their blood and low levels of cysteine. Newborn screening testing detects some HCU patients but most are missed. Patients are frequently diagnosed later in life due to developmental delays in adolescence or in conjunction with medical emergencies in adulthood. The earlier a patient is diagnosed and proper treatment started to keep homocysteine levels as close to normal as possible, the less likely a patient is to have a poor clinical outcome. Unfortunately, it is believed that many patients remain undiagnosed and untreated or undertreated.

What should I do if my homocysteine level is high?

If your homocysteine level is high you should speak with your doctor. Your doctor may refer you to a metabolic geneticist who may want to conduct additional testing.

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