Leigh syndrome or commonly known as leigh’s disease is an inherited neurometabolic disorder characterized by progressive degeneration of the central nervous system (brain, optic nerves, and spinal cord). It usually affects infants between the age of three months and two years, however, teenagers and adults may suffer from this disease as well.
Leigh syndrome is caused by a defect in the function of mitochondria within the cells of the body. Mitochondria are the energy factories of the cells, which convert energy of glucose and fatty acids into a substance called Adenosine triphosphate (ATP). The energy stored in the ATP is then used to perform almost all of the cell’s metabolic functions.
Mitochondria also carry its own DNA, called mitochondrial DNA (mtDNA). When irregular mutations take place in the mitochondrial DNA, the mitochondria become fail to function properly, which in turn affects the central nervous system and causes progressive degeneration of motor functions.
There is also a form of Leigh syndrome called X-linked leigh’s disease which is result from mutations in a gene that produces other group of substances that are essential for cell metabolism.
In X-linked leigh’s disease, genetic mutations occur on the x (female) chromosome. Males have one X chromosome and one Y chromosome, so a mutated gene on the X chromosome is sufficient to cause leigh syndrome. Females have two X chromosomes, so a mutated gene on one X chromosome generally have less effect on a woman because of the non-mutated copy of the same gene on the other X chromosome.
A woman with a gene mutation on one X chromosome will be a carrier. On average, 50% of her sons will inherit the mutation and develop leigh syndrome, and 50% of her daughters will inherit the mutation and become a carrier.