MELAS Syndrome - Causes, Symptoms, Diagnosis, and Treatment

Introduction:

MELAS is the most common type of mitochondrial disease. Mitochondria is the powerhouse of each cell. It is present more in numbers, and the primary function includes converting food substances to energy. The various organs in the body require energy to function correctly. Mitochondrial diseases are inherited and lead to a lack of energy production and thus affecting the body organs.

What Is MELAS?

MELAS is abbreviated as mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes. It affects the nervous system and the muscles of the body. The symptoms appear in children or young adults, worsening in early adulthood.

The following names also mean the same:

• Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes.

• MELAS syndrome.

• Myopathy, mitochondrial-encephalopathy-lactic acidosis-stroke.

How Common Is MELAS?

Mitochondrial disease occurs in one in 4000 individuals. MELAS is one of the mitochondrial diseases and affects men and women equally. The symptoms develop between 2 years to 15 years of age.

What Causes MELAS?

• Genetic alteration or mutations in the mitochondrial DNA (molecule carrying genetic information) is the leading cause of MELAS. Such mutations are transferred to children only from the mother as the mitochondrial DNA present in the sperm cells vanishes during fertilization (union of egg and sperm). The alteration in the mitochondrial DNA affects the mother, and she transfers it to all her children. The symptoms appear in children only if more mitochondrial DNA is defective.

• Mutations in the POLG1 gene also rarely cause MELAS syndrome.

What Are the Signs and Symptoms?

The signs and symptoms rarely appear during childhood. They can develop during infancy. In such a case, it delays growth and leads to poor weight gain and deafness.

The clinical features in children are listed below:

• Recurrent migraine-like headaches.

• Anorexia.

• Vomiting.

• Short stature.

• Myopathy is characterized by the disease affecting the muscle responsible for voluntary movements. It causes muscle weakness or the inability to perform physical exercise. The neurological symptoms are more severe than myopathy.

• Seizures (abnormal brain activity) also develop. It can be focal, where one area of the brain is affected, or generalized, in which all areas of the brain are affected. Stroke-like episodes characterize the seizures. It occurs due to nitric oxide deficiency in the brain's blood vessels. It differs clinically and on imaging from that of typical strokes.

• The children develop muscle weakness on one side (hemiparesis), speech difficulties, and partial blindness (hemianopia). The symptoms worsen in adolescence and early adulthood, leading to hearing loss, impaired vision, and motor function.

• Encephalopathy is a brain disorder that causes mental deterioration leading to impairment of memory, reasoning, and other intellectual abilities. It begins in childhood and progresses later. Loss of consciousness is also seen.

• Other systemic features include fatigue, depression, cardiomyopathy, diabetes, and gastrointestinal and kidney disorders.

• Lactic acidosis refers to the build-up of lactic acid in the blood, brain, and spinal cord fluid, leading to fatigue, vomiting, abdominal pain, muscle weakness, and breathing difficulties.

How Is MELAS Diagnosed?

The cardinal features that are looked at during the diagnosis of MELAS are as follows:

• Stroke-like seizures in individuals less than 40 years of age.

• Encephalopathy features associated with seizures and memory loss.

• Lactic acidosis.

These features are diagnosed using the following techniques:

• Magnetic resonance imaging (MRI) - It helps diagnose lesions in various brain areas. The lesions remain confined to the occipital and parietal lobes of the brain and later involve other regions (cerebellum, thalamus, etc.)

• Magnetic resonance spectroscopy (MRS) is a non-invasive method of measuring different chemical compounds in brain tissues. In patients with MELAS, the affected areas of the brain show increased lactate concentration.

• Genetic testing is the only gold standard test for diagnosing of MELAS syndrome. Mitochondrial DNA mutations can usually be detected in white blood cells and other tissue samples such as skin, hair follicles, urinary sediment and skeletal muscle.

• Blood examination measures the level of lactate and pyruvate. In addition, MELAS syndrome increases the serum concentration of lactic acid.

• Electrocardiogram evaluates the abnormal heart rhythm in children with MELAS.

• Muscle biopsy is the surgical removal of small muscle tissue to evaluate any disorder. The muscle tissue in MELAS shows ragged red fibers.

What Are the Other Similar Disorders?

• Kearns- Sayre Syndrome is a rare systemic disease that affects many body parts. The eye is more commonly affected, leading to weakness and paralysis of eye muscles. It also causes drooping of eyelids, impaired eye movement, and vision loss. The patient also suffers from muscle weakness in limbs, short stature, memory loss, and kidney abnormalities.

• MERRF Syndrome (myoclonic epilepsy with ragged red fibers) is a mitochondrial disease. It causes sudden jerking of arms and legs, muscle weakness, seizures, impaired coordination, vision impairment, and hearing loss. It also shows characteristic red-ragged muscle fibers on biopsy.

• Leigh Syndrome is a rare neuromuscular disorder that causes degeneration of the brain, spinal cord, and optic nerve. The symptoms usually develop in the first year of life. The classical signs include vomiting, diarrhea, and difficulty swallowing during infancy. Lack of weight gain, muscle weakness, paralysis of eye muscles, and breathing difficulties are a few other symptoms of Leigh syndrome.

Can MELAS Be Treated?

No specific treatment is available to control the disease progression. However, the symptoms can be managed as follows:

• Anti-epileptic medications like Carbamazepine, Phenytoin, etc., are used in treating seizures. But the use of Valproate has been found to worsen epilepsy.

• Coenzyme Q10 or L-carnitine are used to delay the effects of MELAS syndrome. It increases the energy production of mitochondria in cells.

• Intravenous administration of L-arginine is used during stroke-like episodes to improve the symptoms and reduce episodes' recurrence.

• L-citrulline is used to increase nitric oxide levels and thus reduce stroke risk.

• Cochlear implants are surgically placed electronic devices that partially restore hearing in children and adults with severe hearing loss.

Conclusion:

MELAS syndrome is an infrequent disorder, but the progression of symptoms is high. The neurological symptoms in children get worse during adulthood. Therefore interprofessional team effort is essential in providing necessary medications and physical therapy to improve the symptoms and standard of living.