Leigh’s disease

Alternative Name :Subacute Necrotizing Encephalomyelopathy (SNEM)

Definition:
Leigh’s disease is a rare neurometabolic disorder that affects the central nervous system.  This progressive disorder begins in infants between the ages of three months and two years. Rarely, it occurs in teenagers and adults. Leigh’s disease can be caused by mutations in mitochondrial DNA or by deficiencies of an enzyme called pyruvate dehydrogenase. Symptoms of Leigh’s disease usually progress rapidly. The earliest signs may be poor sucking ability,and the loss of head control and motor skills.These symptoms may be accompanied by loss of appetite, vomiting, irritability, continuous crying, and seizures. As the disorder progresses, symptoms may also include generalized weakness, lack of muscle tone, and episodes of lactic acidosis, which can lead to impairment of respiratory and kidney function.
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In Leigh’s disease, genetic mutations in mitochondrial DNA interfere with the energy sources that run cells in an area of the brain that plays a role in motor movements. The primary function of mitochondria is to convert the energy in glucose and fatty acids into a substance called adenosine triphosphate ( ATP). The energy in ATP drives virtually all of a cell’s metabolic functions. Genetic mutations in mitochondrial DNA, therefore, result in a chronic lack of energy in these cells, which in turn affects the central nervous system and causes progressive degeneration of motor functions.
There is also a form of Leigh’s disease (called X-linked Leigh’s disease) which is the result of mutations in a gene that produces another group of substances that are important for cell metabolism. This gene is only found on the X chromosome.

It is named after Denis Archibald Leigh, a British psychiatrist who first described the condition in 1951

Symptoms:
The symptoms of Leigh’s disease usually begin between the ages of 3 months and 2 years. Since the disease affects the central nervous system, symptoms may include:

•poor sucking ability
•difficulty holding up the head
•losing motor skills the infant had such as grasping a rattle and shaking it
•loss of appetite
•vomiting
•irritability
•continuous crying
•seizures
As Leigh’s disease becomes worse over time, the symptoms may include:
•generalized weakness
•lack of muscle tone (hypotonia)
•episodes of lactic acidosis (accumulation of lactic acid in the body and brain) that may impair breathing and kidney function
•heart problems

Causes:
It is an inherited disorder that usually affects infants between the age of three months and two years, but, in rare cases, teenagers and adults as well. In the case of the disease, mutations in mitochondrial DNA (mtDNA) or in nuclear DNA (gene SURF1  and some COX assembly factors) cause degradation of motor skills and eventually death.

Mitochondria are an essential organelle in eukaryotic cells. Their function is to convert the potential energy of glucose, amino acids, and fatty acids into adenosine triphosphate (ATP). Mitochondria carry their own DNA, called mitochondrial DNA [mtDNA]. The information stored in the mtDNA is used to produce several of the enzymes essential to the production of ATP.

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Mutations in the mtDNA that cause the mitochondria to fail, to function improperly, a person is at risk for a number of disorders, including Leigh’s disease. In the case of Leigh’s disease, crucial cells in the brain stem have mutated mtDNA, creating poorly functioning mitochondria. This causes a chronic lack of energy in the cells, which, in turn, affects the central nervous system and inhibits motor functions.

Diagnosis:
Diagnosis of Leigh’s disease is based on the symptoms the infant or child has. Tests may show a deficiency of pyruvate dehydrogenase or the presence of lactic acidosis. Individuals with Leigh’s disease may have symmetrical patches of damage in the brain that may be discovered by brain scan. In some individuals, genetic testing may be able to identify the presence of a genetic mutation.

Treatment:
Leigh’s disease is a extremely rare disorder, and there is currently no cure, nor effective treatment. It usually affects infants under two years of age, but, in rarer cases, teenagers and adults as well. A high-fat, low-carbohydrate diet may be recommended. Adults may have puffiness and/or swelling of the eye area and the hands. It is currently treated with thiamin (vitamin B1), but even with treatment, infants rarely live longer than two or three years after the onset of the disease. In cases of older people, the disease takes longer, but is still almost always fatal.

Drug treatments may be needed for epilepsy, movement problems, and cardiac or renal complications.

Prognosis:
The prognosis for individuals with Leigh’s disease is poor. Individuals who lack mitochondrial complex IV activity and those with pyruvate dehydrogenase deficiency tend to have the worst prognosis and die within a few years. Those with partial deficiencies have a better prognosis, and may live to be 6 or 7 years of age. Some have survived to their mid-teenage years.

Resrarch:
The NINDS supports and encourages a broad range of basic and clinical research on neurogenetic disorders such as Leigh’s disease. The goal of this research is to understand what causes these disorders and then to apply these findings to new ways to diagnose, treat, and prevent them.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose

Resources:
http://www.bbc.co.uk/health/physical_health/conditions/leigh1.shtml
http://rarediseases.about.com/od/mitochondrialdiseases/a/leighsdisease.htm
http://www.ninds.nih.gov/disorders/leighsdisease/leighsdisease.htm
http://en.wikipedia.org/wiki/Leigh’s_disease
http://baby-braden.blogspot.com/2008/10/diagnosis-leighs-disease.html

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