Mitochondrial encephalopathy, lactic acidosis, and stroke syndrome (MELAS) is caused by mitochondrial DNA mutations, leading to insufficient energy production and multisystem problems. Symptoms can affect the central nervous, cardiac, and skeletal muscle systems, as well as the pancreas, liver, and kidneys. Diagnosis involves imaging studies, blood and spinal fluid tests, and cell studies, and treatment is individualized with a regimen of antioxidants, amino acids, and vitamins.
Mitochondrial encephalopathy, lactic acidosis, and stroke syndrome (MELAS) occurs when mitochondrial deoxyribonucleic acid (DNA) mutates, causing cells to produce insufficient energy. Patients can acquire the syndrome, but the disorder often passes from the mother. The age of onset varies, with patients experiencing symptoms as early as three months of age, while others have no problems until over 60 years of age. However, most people who have the syndrome experience symptoms before the age of 20. Because all cells in the body contain mitochondria, symptoms secondary to the syndrome can occur anywhere in the body, but are usually multisystem problems.
Cells typically contain hundreds to thousands of organelles known as mitochondria. The structures produce energy through an electron transport chain, which synthesizes proteins into adenosine triphosphate (ATP). DNA mutations that occur in the mitochondria disrupt several components of this chain, inhibiting the formation of ATP. Patients diagnosed with mitochondrial encephalopathy commonly have mitochondria containing normal DNA and others with mutated DNA. In an effort to compensate for the insufficient energy production, the abnormal mitochondria replicate into more mitochondria, which also contain the genetic mutation.
Mitochondrial cytopathy also triggers compensation for insufficient energy production using other metabolic processes. The body generally synthesizes glucose into pyruvate and lactic acid during exercise, but in mitochondrial encephalopathy these processes occur at rest, resulting in lactic acidosis. Lack of sufficient cellular energy combined with the byproducts of metabolic processes produces a buildup of toxins, which leads to cellular damage and destruction. The researchers also found that the patients display an abnormal amount of intracellular calcium, causing an increase in cell membrane excitability.
The organs and systems most affected by the syndrome are those that require the greatest amount of energy. Patients generally experience symptoms affecting the central nervous system, cardiac and skeletal muscles. The pancreas, liver and kidneys can also be affected.
Central nervous system symptoms associated with mitochondrial encephalopathy include dementia, seizures, and stroke-like abnormalities that occur as a result of lesions forming in the brain. The syndrome can also affect sensory nerves, causing blindness or deafness. Damage or destruction of neural and muscle tissues commonly produces loss of muscle tone, spasticity, and abnormal body movements. Affected heart cells can cause conduction disruptions, leading to an irregular heart rate. Involvement of the pancreas often leads to diabetes.
Leigh syndrome, a variety of mitochondrial myopathy also known as subacute necrotizing encephalomyelopathy, affects children aged 3 to 12 months and often materializes after a viral infection. In addition to affecting the central nervous system and muscle tissue, the disorder commonly involves the cardiac and respiratory systems. Young children who have the disease often die by age three from heart or respiratory failure.
Specialists diagnose mitochondrial encephalopathy using imaging studies, blood and spinal fluid tests, and cell studies. Magnetic resonance imaging (MRI) usually reveals infarct-like lesions, or dead tissue, not associated with vascular structures. Lesions usually develop most frequently in the back of the brain. Abnormalities in blood and spinal fluid usually include increased levels of the amino acid alanine and lactic acid. Cells taken from muscles reveal red, irregular-looking fibers.
Cellular samples obtained from inside the mouth and skin generally contain mitochondria with defective DNA. Doctors typically treat patients on an individual basis because symptoms vary from patient to patient and affect different body systems. Doctors often prescribe a regimen of antioxidants, amino acids and vitamins.
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