The clinical course is very variable. Common problems in young children include poor weight gain and floppiness. Most patients have problems by the age of 2 years, deteriorate rapidly and die within a year or two. In the vast majority of patients, there is no effective treatment. Diagnosis of Leigh syndrome is difficult.
Scans usually show changes in parts of the brain called the brainstem and basal ganglia.
In rare cases, Leigh Syndrome may begin during late adolescence or early adulthood. Here the progression of the disease is slower than that in children. Inheritance patterns Leigh syndrome is caused by defects in the cell's pathway for producing energy. This process occurs in parts of the cell called mitochondria. This is available in some cases of Leigh syndrome.