What is Leigh Syndrome, French-Canadian Type? There are multiple forms of Leigh syndrome, with more than 30 causative genes identified. However, Leigh syndrome, French-Canadian type (LSFC) is exclusively caused by harmful genetic changes (mutations) in the LRPPRC gene. Individuals with LSFC often appear unaffected at birth, but begin to lose basic skills such as head control, sucking, walking, and talking in infancy or early childhood. They may also present with intellectual disabilities, differences in facial features, irritability, vomiting, and seizures. The symptoms associated with this condition are the result of damage (lesions) that develop in the brain, specifically the midbrain and/or brainstem. The cells in these regions of the brain also begin to lose their protective coating (myelin sheath), which decreases the brain's ability to process information, respond to stimuli, and initiate muscle movement. In addition, LSFC often causes periods of low blood sugar and often causes the build-up of toxic substances in the blood (metabolic crisis), which can lead to vomiting, diarrhea, extreme sleepiness, irritable moods, and behavior changes. These symptoms may rapidly worsen, ultimately leading to significant breathing difficulties, heart problems, and vision loss. How common is Leigh Syndrome, French-Canadian Type? LSFC has never been reported outside of the French-Canadian population. Among those from the Saguenay-Lac Saint Jean region of Quebec, the disorder is observed in approximately 1 in 2,000 births. How is Leigh Syndrome, French-Canadian Type treated? Currently, there is no cure for LSFC, and treatment is only supportive, with the goal of alleviating symptoms as they arise. Medications may be provided for treatment of seizures, cardiac, metabolic, and respiratory issues, and for muscle and movement disorders as they develop. What is the prognosis for an individual with Leigh Syndrome, French-Canadian Type? Typically, symptoms of Leigh syndrome present during the first year of life and progress rapidly. The average life expectancy for children with LSFC is approximately five to six years. However, some individuals do not develop symptoms until adulthood and/or have a slowly progressing course of the disorder. Other names forLeigh syndrome, French-Canadian type Cox deficiency, French-Canadian type Cox deficiency, Saguenay-Lac Saint Jean type Cytochrome C oxidase deficiency LSFC Leigh syndrome due to mtDNA mutations Leigh syndrome, Saguenay-Lac Saint Jean type Respiratory complex chain deficiency type IV mtDNA-associated Leigh syndrome and NARP References Debray et al., 2011, J Med Genet, 48(3):183-9, PMID: 21266382 Laberge et al., 2005, Clin Genet, 68(4):287-301, PMID: 16143014 Merante et al., 1993, Am J Hum Genet, 53(2):481-7, PMID: 8392290 Mootha et al., 2003, Proc Natl Acad Sci USA, 100(2):605-10, PMID: 12529507 Morin et al., 1993, Am J Hum Genet, 53(2):488-96, PMID: 8392291 Olahova et al., 2015, Brain, 138(12):3503-19, PMID: 26510951 Rahman et al., 1996, Ann Neurol, 39(3):343-51, PMID: 8602753 Thompson Legault et al., 2015, Cell Rep, 13(5):981-9, PMID: 26565911