What is Leigh Syndrome?

Overview

Leigh Syndrome (also known as Leigh’s Disease, Leigh necrotizing encephalopathy, Maternally Inherited Leighs, Classical Leigh Syndrome) is a genetically inherited mitochondrial disorder that usually presents in a child’s first year of life. Mitochondria are the body’s power houses and are responsible for processing and providing energy for each cell in the body. In people with Leigh Syndrome, 90% or more of their mitochondria will carry a genetic mutation that means their cells cannot function correctly.

Leigh Syndrome is a neurological disorder because the main areas to be affected are the child’s brain functioning and development. This is because the brain is the most power-hungry organ in the human body and requires a lot of energy to function. As someone does not have the energy stores to power the brain efficiently this impacts the child’s ability to reach developmental milestones and they gradually lose their ability to move or do things they may have done previously (e.g. crying, sitting, kicking legs etc.).

Signs and Symptoms of Leigh Syndrome

Feeding problems are usually one of the first signs of Leigh Syndrome (e.g. difficulty swallowing, vomiting, reflux-like symptoms) and this impacts the child’s ability to grow as expected. Doctor’s define this as a failure to thrive. Other common symptoms include muscle weakness and problems with moving the body, involuntary movement in the muscles and loss of sensation in the limbs. Issues with development, as mentioned above, are also one of the most noticeable symptoms.

Because mitochondria power the cells in all the major organs of the body, people with Leighs Syndrome may experience a range of other symptoms including: involuntary eye movements or issues receiving information to the eyes from the brain, breathing issues, and thickening of heart muscle which makes it harder to pump blood around the body. People with Leigh Syndrome often have higher levels of lactate in the body which can affect respiratory. Kidney and psychomotor functioning. Seizures can sometimes also occur in people with Leigh Syndrome as well as involuntary movements.

What causes Leigh Syndrome?

Leigh Syndrome is a genetic condition inherited from the child’s parents. It is caused by a mutation in the person’s genes. More specifically, it effects one of the many types of genes responsible for processing proteins in the body (e.g. complex I, SURFI, ATP6), so for each individual it may affect a different gene or combination of genes. In 20% of Leigh Syndrome cases the mutation occurs in the mitochondrial DNA (mtDNA) that is passed on through the mother’s egg (maternally inherited). In the remaining 80% of cases the mutation occurs in the nuclear DNA which includes the combination of genes inherited from the mother and father.

Diagnosing Leigh Syndrome

Leigh Syndrome is usually diagnosed following a series of tests. An MRI scan is usually performed to determine brain structure, particularly in the basal ganglia, brainstem and spinal cord. Blood tests and a lumbar puncture may be performed to determine blood lactate levels. Genetic testing (usually from a blood sample but sometimes from a skin or muscle biopsy) is also used to determine a diagnosis of Leigh Syndrome.

What is the prognosis for Leigh Syndrome?

The first symptoms of Leigh Syndrome usually present before a child is one years old. The progressive nature of Leigh Syndrome means that children with Leigh syndrome rarely live past their third birthday. The most common reason for death is respiratory issues. Children with Leigh syndrome need to be very careful if they pick up a virus or infection as they may not have the energy reserves to fight these illnesses whilst performing important daily functioning. In rare cases onset of Leigh Syndrome may occur in adolescence or adulthood.

Treating Leigh Syndrome

Unfortunately, there is currently no cure for Leigh Syndrome. Specific symptoms of Leigh disease may be treated and a person may regularly see a team of neurologists, paediatricians, nurses and other consultants and health professionals. For example, patients may work with a dietician, feeding specialists or speech and language therapists to monitor and treat feeding issues and a feeding tube may be required. Physiotherapy, occupational therapy and assisted devices such as chairs or prams may be prescribed to help with muscle weakness. Vitamins (particularly B vitamins) may be prescribed to people with Leigh syndrome.

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