Homocystinuria

Homocystinuria is a rare genetic disorder characterized by an elevated level of homocysteine in the blood and urine. It is caused by a deficiency in one of several enzymes involved in the metabolism of the amino acid methionine.

Causes

Homocystinuria is typically inherited in an autosomal recessive pattern, meaning that a person must inherit two copies of the mutated gene (one from each parent) to develop the condition. The most common cause of homocystinuria is a deficiency in cystathionine beta-synthase (CBS), which is responsible for converting homocysteine to cystathionine.

Symptoms

The symptoms of homocystinuria can vary widely, but may include:

• Dislocation of the lens in the eye (ectopia lentis)
• Glaucoma
• Cataracts
• Osteoporosis
• Skeletal abnormalities, such as scoliosis or osteopenia
• Cardiovascular problems, including blood clots and stroke
• Thromboembolic events
• Cognitive impairment or developmental delay
• Seizures

Diagnosis

Homocystinuria is typically diagnosed through a combination of:

• Newborn screening tests, which measure the level of homocysteine in the blood
• Urine tests, which detect the presence of homocysteine and other abnormal metabolites
• Genetic testing, which identifies mutations in the CBS gene or other genes involved in methionine metabolism
• Enzyme assays, which measure the activity of CBS and other enzymes involved in homocysteine metabolism

Treatment

Treatment for homocystinuria typically involves a combination of:

• Dietary restrictions, such as a low-methionine diet or a vegan diet
• Supplementation with vitamins B6, B12, and folate, which help to reduce homocysteine levels
• Betaine supplements, which can help to reduce homocysteine levels
• Medications, such as anticoagulants or antiplatelet agents, to prevent blood clots and cardiovascular problems

Complications

If left untreated, homocystinuria can lead to a range of complications, including:

• Cardiovascular disease
• Stroke or transient ischemic attack (TIA)
• Blood clots or thromboembolic events
• Osteoporosis and fractures
• Cognitive impairment or dementia
• Seizures or other neurological problems

Prognosis

The prognosis for individuals with homocystinuria varies widely, depending on the severity of the condition and the effectiveness of treatment. With early diagnosis and treatment, many people with homocystinuria can lead active and healthy lives.