HOMOCYSTINURIA
Homocystinuria is a rare condition that keeps the body from breaking down and processing protein, specifically an amino acid called methionine.
- Amino acids are the building blocks of protein; they are organic compounds that combine to form protein
- Amino acids also serve as intermediates in metabolism
- They play a central role in sustaining the health of a human body because they largely promote hormones production, muscles structure, nervous system, and cellular functioning
- Amino acids are classified into essential, nonessential and, conditional amino acids
- Nonessential amino acids are produced by our body, while essential amino acids are not produced by our body and so must come from food
- The amino acid involved in homocystinuria is methionine, which is one of the essential amino acids
- Methionine is a naturally occurring protein that infants need for growth and adults need to maintain their body’s nitrogen balance
- The inability of the body to break down methionine as seen in homocystinuria can be toxic and cause damage to the nervous system
- If left untreated, the disorder can have serious and sometimes fatal complications, including a reduced life expectancy
- It is known that before the age of 30, almost 75% of patients with untreated homocystinuria die from thrombotic complications such as heart attack.
CAUSES
Homocystinuria is caused by the deficiency of the enzyme that breaks down methionine. An individual with the disorder either doesn’t make this enzyme or the enzyme is not just working right. Certain genetic mutations present at birth causes this to happen. Mutations in the cystathionine beta-synthase (CBS) gene cause the most common form of the condition.
Rarely homocystinuria may be caused by mutations in several other genes, including MTHFR, MTR, MTRR, and MMADHC.
Homocystinuria is inherited in the autosomal recessive pattern, this means that a child must inherit the defective gene from both parents to be affected.
SYMPTOMS
Symptoms are evident in the first year of life. The disorder affects children differently. While some children are mildly affected, symptoms may worsen as they progress into adulthood.
Symptoms may include:
- Weak bones
- Chest deformities
- Pale skin and hair
- Spinal curvature
- Nearsightedness and dislocated eye lenses
- Long and thin arms and legs
- Slow weight gain and growth
- Developmental delays
- Learning disabilities
- Behavioral problems
- Blood clots
- Seizures
- Megablastic anemia, an anemia characterized by larger than normal red blood cells
DIAGNOSIS AND TREATMENT
To make a diagnosis, the doctor will look for certain symptoms. Clear symptoms that may lead a doctor to test for the disorder is if a child is extremely thin or too tall for their age, or not growing as expected.
Additionally, the doctors may look for signs of dislocated eye lenses, chest deformity, and spinal curvature.
An eye examination may reveal a dislocated eye lens, and X-rays may indicate signs of weak bones.
Other diagnostic procedures include genetic screening, liver enzyme tests, liver biopsies, and amino acid testing.
TREATMENT
No cure exists for the condition although it can be treated with supplements, diet restrictions, and medications.
The doctor may recommend high doses of B6 supplements. Most of the people with the disorder may have to take these supplements for the rest of their lives.
If vitamin B6 doesn’t work, the doctor may recommend a low-methionine diet. Examples of food that contain high levels of methionine include:
- Eggs
- Soy
- Dairy
- Nuts and beans
- Some meat and fish
- Regular Flour
Fruits and veggies may be consumed in low, controlled quality because they contain small amounts of methionine.
There are foods, such as flour, pasta, and bread, that are low in methionine made specifically for people with the disorder.
The doctor may also recommend betaine. Taking folic acid with betaine may also help.