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MELAS: Causes, Symptoms and Treatment

MELAS is a rare mitochondrial disease affecting muscles, the brain, and nerves. It is characterized by stroke-like episodes, muscle weakness, and neurological symptoms.

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MELAS is a rare mitochondrial disease affecting muscles, the brain, and nerves. It is characterized by stroke-like episodes, muscle weakness, and neurological symptoms.

What is MELAS?

MELAS stands for Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like Episodes. It is a rare, genetically determined disease caused by dysfunctions of the mitochondria – the energy-producing organelles of cells. MELAS belongs to the group of mitochondrial diseases and primarily affects tissues with high energy demands, such as the brain, muscles, and heart.

Causes

The disease is caused by mutations in mitochondrial DNA (mtDNA). In the majority of cases, a point mutation at position 3243 in the gene encoding mitochondrial transfer RNA (tRNA) for leucine is responsible (m.3243A>G). This mutation disrupts protein synthesis within the mitochondria and leads to reduced production of ATP (adenosine triphosphate), the primary energy carrier of cells.

Mitochondrial DNA mutation (most common: m.3243A>G in over 80% of cases)
Less commonly: other mtDNA mutations such as m.3271T>C or m.3252A>G
Inheritance occurs exclusively through the maternal line (maternal inheritance)
Spontaneous new mutations are also possible

Symptoms

MELAS typically presents in childhood or early adulthood, although onset can vary. The disease often follows an episodic course and progresses over time.

Cardinal Symptoms

Stroke-like episodes: Sudden neurological deficits such as vision loss, hemiplegia, or speech disturbances that cannot be explained by vascular occlusions
Lactic acidosis: Elevated lactate levels in the blood and cerebrospinal fluid due to impaired energy metabolism
Encephalopathy: Cognitive impairment, confusion, and dementia
Myopathy: Muscle weakness and exercise intolerance

Additional Symptoms

Epileptic seizures
Migraine-like headaches
Sensorineural hearing loss
Short stature
Diabetes mellitus
Cardiac arrhythmias and cardiomyopathy
Visual disturbances (e.g., ptosis, optic atrophy)

Diagnosis

Diagnosing MELAS requires a combination of clinical evaluation, imaging, and molecular genetic testing.

Blood and cerebrospinal fluid analysis: Elevated lactate and pyruvate levels
Brain MRI: Detection of stroke-like lesions that do not correspond to a specific vascular territory
Genetic testing: Identification of mtDNA mutation in blood, urine, or muscle tissue
Muscle biopsy: Detection of "ragged red fibers" as a characteristic histological finding
Enzyme activity measurement: Detection of defects in the respiratory chain complexes in muscle tissue

Treatment

There is currently no curative therapy that corrects the underlying genetic mutation. Treatment is symptom-oriented and aims to reduce complications and improve quality of life.

Pharmacological Approaches

L-Arginine: An amino acid that promotes vasodilation and may reduce the severity of stroke-like episodes
L-Citrulline: Used as an alternative or supplement to L-Arginine
Coenzyme Q10 (Ubiquinone): Supports the mitochondrial respiratory chain
Riboflavin (Vitamin B2), Thiamine (Vitamin B1): As cofactors for energy metabolism
Antiepileptic drugs: For the management of epileptic seizures (valproate should be avoided due to potential mitochondrial toxicity)

Supportive Measures

Hearing aids for hearing impairment
Physical therapy and occupational therapy
Neurological rehabilitation following stroke-like episodes
Regular cardiological and ophthalmological monitoring
Diabetes management

Prognosis and Disease Course

MELAS is a chronically progressive disease. The clinical course is highly variable and depends, among other factors, on the proportion of mutated mitochondrial DNA in different tissues (known as heteroplasmy). Recurrent stroke-like episodes can lead to increasing cognitive impairment, dementia, and physical disability. Early diagnosis and consistent symptomatic treatment can positively influence the course of the disease.

References

El-Hattab AW, Adesina AM, Jones J, Scaglia F. MELAS syndrome: Clinical manifestations, pathogenesis, and treatment options. Molecular Genetics and Metabolism, 116(1-2):4-12, 2015. PubMed PMID: 26095523.
Pavlakis SG, Phillips PC, DiMauro S, De Vivo DC, Rowland LP. Mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes: a distinctive clinical syndrome. Annals of Neurology, 16(4):481-488, 1984.
Orsucci D, Angelini C, Bertini E et al. Revisiting mitochondrial ocular myopathies: a study from the Italian Network. Journal of Neurology, 264(8):1777-1784, 2017.

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