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Without symptoms or genetic tests, parents have no way of knowing if they are carriers until it's too late--after they give birth to a child with the disease. One in 23 inhabitants of this region are estimated to be carriers.

Scientists have known that this genetic defect of unknown origin causes malfunctioning in mitochondria (tiny energy factories in the cell) that results in defects in energy metabolism and symptoms of mental retardation and a dangerous accumulation of toxic lactic acid in the blood that leads to coma. These episodes can occur anytime between 6 months to 11 years of age. Often this metabolic crisis is the first indication that an outwardly happy child has the disease. One third of the children don't survive the first crisis and those who do survive end up having a second or third crisis that is fatal.

Physicians in the SLSJ region first began noticing the disease in the 1990s and began to see a pattern that suggested this was a genetic disease. In 1993, Charles Morin, a pediatrician who had treated many affected children, showed in collaboration with Brian Robinson of the Toronto Hospital for Sick Children that the symptoms were caused by a deficiency in an enzyme called cytochrome c oxidase (COX) that prevents proper energy metabolism. But the genetic defect underlying this deficiency still remained unknown.

Scientists then began to conduct family studies to identify the gene involved. In 1997, Morin, Robinson, and Whitehead's Rioux began a collaboration to search for the gene. In 2001, the group led by Whitehead narrowed the search for the gene to a region on the short arm of chromosome 2, but an analysis of the known genes in that region found that none of the genes were involved in mit
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Contact: Christine Zeindler
christine.zeindler@muhc.mcgill.ca
514-934-1934
McGill University
14-Jan-2003