Introduction

Leigh Syndrome, a rare mitochondrial disorder, affects approximately 1 in 40,000 live births and is characterized by the degeneration of the central nervous system. Symptoms typically appear between three months and two years of age, but can manifest later in life. The syndrome is caused by mutations in mitochondrial or nuclear DNA, with over 75 different gene mutations identified. Diagnosis involves clinical evaluation, imaging scans, blood and cerebrospinal fluid tests, and genetic testing. While there is no cure, treatment focuses on managing symptoms and slowing disease progression through supportive care, specific treatments, and assistive technology. Ongoing research aims to better understand the genetic mechanisms underlying Leigh Syndrome and develop targeted treatments.

Leigh Syndrome

Formal Name: Subacute Necrotizing Encephalomyelopathy

Demographic Information

• Incidence: Approximately 1 in 40,000 live births globally, with higher incidences in specific populations such as the Faroe Islands.
• Prevalence: Rare, but exact prevalence is difficult to determine due to underdiagnosis.
• Gender: Affects both males and females equally.
• Onset Age: Symptoms typically appear between the ages of three months and two years, but can manifest later in childhood, adolescence, or even adulthood.

Coding

• ICD-11: 8A41.1
• ICD-10-CM: G31.82
• OMIM: 256000 - Leigh Syndrome
• UMLS: C0023195
• MeSH: D007834
• GARD: 6385

Medical Features and Pathophysiology

• Etiology: Leigh Syndrome is primarily a mitochondrial disorder caused by mutations in either mitochondrial DNA (mtDNA) or nuclear DNA (nDNA) that affect mitochondrial function. Over 75 different gene mutations can cause the condition, with the most common being in the MT-ATP6 gene. These mutations impair the complexes of the mitochondrial respiratory chain, leading to deficient energy production in cells, particularly affecting high-energy tissues like the brain and muscles.
• Pathology: The disease is characterized by the degeneration of the central nervous system, including the brainstem, basal ganglia, cerebellum, and spinal cord. This degeneration results in progressive neurological deterioration, which is the hallmark of Leigh Syndrome.

Clinical Information

Core Characteristics

• Etiology: Genetic
• Pathology: Heritable
• Rarity Classification: Orphan
• Typical Onset: Early Infancy
• Gender Impact: Either Gender
• Progressive/Degenerative: Yes
• Seizure Prevalence: Yes (>90%)
• Population Trend: Unknown

Pathophysiology

Over 75 genes implicated, including mitochondrial DNA, but 80% of cases appear to be familial (autosomal recessive). Rarely somatic or de novo.

AAC Considerations

Additional Clinical Notes

Neurodegenerative disorder in infants, pretty conclusively quickly fatal, definitely requiring AAC but few make it past age 3. Interestingly high prevalence in French speaking Canada

Patient Advocacy & Support Organizations

• https://www.umdf.org/
• http://www.mitoaction.org/

Symptoms

Infantile Onset

• Poor sucking ability and difficulty feeding.
• Loss of head control and motor skills.
• Vomiting and irritability.
• Seizures and developmental delay.
• Progressive muscle weakness (hypotonia).
• Episodes of lactic acidosis causing rapid breathing and poor coordination.
• Respiratory issues, which may require ventilatory support.

Juvenile and Adult Onset

• Ataxia (lack of muscle coordination).
• Dysarthria (difficulty speaking).
• Dystonia (involuntary muscle contractions).
• Vision problems including optic atrophy and nystagmus (involuntary eye movements).
• Hearing loss.
• Cognitive decline and dementia.

Diagnosis

• Clinical Evaluation: Based on symptoms and medical history.
• MRI and CT Scans: To identify characteristic lesions in the brain.
• Blood and Cerebrospinal Fluid (CSF) Tests: High levels of lactate can indicate mitochondrial dysfunction.
• Genetic Testing: Confirms mutations in mtDNA or nDNA related to Leigh Syndrome. This can involve testing the blood, muscle, or other tissues to identify specific genetic changes.

Management and Treatment

• Supportive Care: There is no cure for Leigh Syndrome. Treatment focuses on managing symptoms and slowing disease progression.

- Nutritional Support: Including supplements like coenzyme Q10, thiamine, and riboflavin, which can support mitochondrial function. In cases of feeding difficulty, a gastrostomy tube may be necessary. - Respiratory Support: Non-invasive ventilation or tracheostomy for severe respiratory muscle weakness. - Physical and Occupational Therapy: To maintain mobility and support daily activities.

• Specific Treatments:

- Pyruvate Dehydrogenase Deficiency: Ketogenic diet and thiamine. - Coenzyme Q10 Deficiency: Supplementation with CoQ10 and other mitochondrial support agents.

Assistive Technology Suggestions

• Mobility Aids: Wheelchairs and walkers to assist with mobility.
• Communication Devices: Augmentative and Alternative Communication (AAC) devices for those with severe speech impairments.
• Environmental Control Systems: Adaptive switches and voice-activated systems to enhance independence in daily activities.

Access Modalities

Access needs change rapidly as the condition progresses. Early intervention may use touch or switch access, but severe motor deterioration often necessitates eye gaze or partner-assisted scanning. Given the young age of onset and limited life expectancy, AAC goals focus on immediate quality of life rather than long-term skill development.

Comprehensive Management and Care Strategies

• Routine monitoring of neurological progression and complications
• Symptom management for spasticity and pain
• Screening for respiratory, cardiac, and nutritional complications

• Counseling for families facing end-of-life care decisions
• Connection to support groups and palliative care resources

Challenges and Considerations

Managing Leigh Syndrome involves complex medical coordination across respiratory, nutritional, and neurological domains. The progressive nature requires anticipatory guidance for families and frequent reassessment of care goals. Most children do not survive past early childhood, making palliative care planning essential.

Future Directions and Research:

• Genetic Research: Ongoing research into the genetic mechanisms underlying Leigh Syndrome to better understand its pathophysiology and develop targeted treatments.
• Clinical Trials: Participation in clinical trials to explore new treatments and therapies, including advances in gene therapy and mitochondrial support therapies.
• Innovative Therapies: Developing advanced therapies to address the underlying causes and symptoms of Leigh Syndrome, such as enzyme replacement therapy and novel drug treatments.

References

1. MedlinePlus Genetics: Provides an overview of Leigh Syndrome, including genetic causes and inheritance patterns. MedlinePlus Genetics 2. National Organization for Rare Disorders (NORD): Detailed information on symptoms, causes, diagnosis, and management. NORD Leigh Syndrome 3. Cleveland Clinic: Overview of causes, symptoms, and treatment strategies. Cleveland Clinic Leigh Syndrome 4. Genetic and Rare Diseases Information Center (GARD): Comprehensive details on Leigh Syndrome, including symptoms and genetic background. GARD Leigh Syndrome 5. Child Neurology Foundation: Discusses diagnosis, treatment options, and ongoing research. Child Neurology Foundation 6. UMDF (United Mitochondrial Disease Foundation): Provides information on support resources, clinical trials, and patient advocacy. UMDF Leigh Syndrome 7. The Brain Charity: Details on symptoms, support services, and resources for those affected by Leigh Syndrome. The Brain Charity

Additional Resources

1. (1951). SUBACUTE NECROTIZING ENCEPHALOMYELOPATHY IN AN INFANT. Journal of Neurology Neurosurgery & Psychiatry. https://doi.org/10.1136/jnnp.14.3.216 [PDF] 2. (1975). Leigh's disease: significance of the biochemical changes in brain. Journal of Neurology Neurosurgery & Psychiatry. https://doi.org/10.1136/jnnp.38.11.1100 [PDF]

Epidemiology and Demographics

Etiology and Pathophysiology

Clinical Features and Stages

Diagnosis

Clinical Recommendations

Care Management

Transition Planning