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Brain Scans

ABOUT Leigh Syndrome

What is Leigh syndrome?

Leigh syndrome also known as Leigh disease, is a mitochondrial disorder that mostly affects children under the age of ten. It is a serious neurological disorder that often affects the development of mobility, posture, and mental capacities in children, with these capabilities occasionally being lost after a period of seemingly normal growth. Leigh syndrome is caused by a variety of genetic errors (mutations).

Who does it affect?

Leigh syndrome affects about 1 out of 77,000 live births, with symptoms often appearing within the first year of life. Though exceedingly unusual, some persons may not show symptoms until they are in their early adult years, while others may show signs gradually throughout infancy.

What are the clinical features?

 Early on in life, the symptoms of LS are generally non-specific and can be confused with a variety of other pediatric diseases (both neurological and non-neurological disorders). Low sucking skills, loss of appetite, and frequent vomiting are among fo the signs which might lead to poor weight gain (failure to thrive). Children with poor head control and spells of unexplained irritation are common in young children. They may also have difficulties meeting developmental milestones.

The gradual development regression is on of Leigh syndrome’s characteristic symptoms (loss of skills) Any previously gained intellectual and physical skills may be lost, particularly when youngsters are sick with mild childhood diseases like stomach bugs or coughs and colds. The movement disorder is another diagnostic sign. Dystonia (stiffness of movement) ataxia (trouble coordinating movement) and difficulty articulating words are only a few examples.

Changes in the basal ganglia and/or brainstem should accompany these movement abnormalities. Lactic acid levels that are abnormally high in the blood, brain, and/or other body tissues are known as


Leigh syndrome is characterized by abnormally high levels of lactic acid in the blood, brain,and/other body tissues. Any kid who exhibits these characteristics should be sent to a pediatric neurologist for confirmation of diagnosis.


Aside from the defining characteristics listed above, LS can affect a variety of systems, albeit not all symptoms are present in all patients. The following are a few (by no means exhaustive) instances.

Generalized weakness, lack of muscle tone (hypotonia), clumsiness, tremors, and muscular spasms are all neurological issues. The development of the nervous system is frequently delayed, and intellectual impairment is widespread. Respiratory issues can range from mild to severe. Apnea (temporary cessation of spontaneous breathing), dyspnea (difficulty breathing), hyperventilation (abnormally rapid breathing) and/or abnormal breathing patterns are all examples of respiratory disorders. Nystagmus (abnormally rapid eye movements), strabismus (crossed eyes), ophthalmoplegia (paralysis for particular eye muscles), optic atrophy (degeneration of the eye nerves) and/or vision impairment leading to blindness are all examples of visual difficulties. Cardiac disorders are extremely rare, however, they can include abnormal heart muscle or fiber expansion. Reflux, vomiting, abdominal discomfort, gastritis, diarrhea, and constipation are all typical gastrointestinal issues.


Adult-onset Leigh syndrome (a very rare variant of the condition) symptoms usually appear during adolescence or early adulthood. In this version of the sickness, the neurological abnormalities linked with the disease progress slowly.

How is it diagnosed?

The diagnosis is frequently suggested by specific patterns of brain involvement on an MRI scan, as well as typical clinical signs. Lumbar puncture (collection of spinal fluid) may also be useful in verifying a mitochondrial function deficit (increased cerebrospinal fluid lactate) and ruling out other medical issues. Muscle biopsy, albeit less common these days, can be useful in verifying that mitochondrial function is incorrect and in directing further precise genetic testing.

What causes Leigh syndrome?

Genetic mutations in approximately over 100 distinct genes can cause LS. Nuclear genes (those found in nuclear DNA) and mitochondrial genes are examples of these (within the mtDNA)

The mitochondrial energy production pathway is disrupted by all mutations. One of mitochondria’s key functions is to transform energy from food (carbohydrates and lipids) into a form that the cell can utilize. The energy chain (complex I though V) is made up of five protein complexes that are required for this energy conversion process. The proteins that make up these complexes or how they are put together are affected by many of the genetic variants that cause Leigh syndrome.

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