Leigh Syndrome is a severe neurological disorder that usually becomes apparent in the first year of life. This condition is characterized by progressive loss of mental and movement abilities (psychomotor regression) and may result in death during childhood, usually due to respiratory failure. A small number of individuals do not develop symptoms until adulthood or have symptoms that worsen more slowly. The first signs of Leigh syndrome seen in infancy are usually vomiting, diarrhea, and difficulty swallowing (dysphagia), which disrupts eating. These problems often result in an inability to grow and gain weight at the expected rate (failure to thrive). Severe muscle and movement problems are common in Leigh syndrome. Affected individuals may develop weak muscle tone (hypotonia), involuntary muscle contractions (dystonia), and problems with movement and balance (ataxia). Loss of sensation and weakness in the limbs (peripheral neuropathy), common in people with Leigh syndrome, may also make movement difficult. Several other features may occur in people with Leigh syndrome, including:
- weakness or paralysis of the muscles that move the eyes (ophthalmoparesis)
- rapid, involuntary eye movements (nystagmus)
- degeneration of the nerves that carry information from the eyes to the brain (optic atrophy)
- severe breathing problems
- hypertrophic cardiomyopathy, which is a thickening of the heart muscle that forces the heart to work harder to pump blood.
- Elevated lactate levels in blood, urine and cerobrospinal fluid
The signs and symptoms of Leigh syndrome are caused in part by patches of damaged tissue (lesions) that develop in the brains of people with this condition as seen on MRI. The brain lesions are often accompanied by loss of the myelin coating around nerves (demyelination), which reduces the ability of the nerves to activate muscles used for movement or relay sensory information from the rest of the body back to the brain.
There are no proven therapies for Leigh syndrome, therefore, treatment recommendations are directed toward the specific symptoms in each individual. Treatment may require the coordinated efforts of a team of specialists. The most common treatment for Leigh syndrome is the administration of thiamine (Vitamin B1) or thiamine derivatives. Some people with this disorder may experience a temporary symptomatic improvement and a slight slowing of the progression of the disease. In those patients with Leigh syndrome who also have a deficiency of pyruvate dehydrogenase enzyme complex, a high fat, low carbohydrate diet may be recommended. Genetic counseling is recommended for families of affected individuals with this disorder. Other treatment is symptomatic and supportive.