French Canadian Leigh syndrome has similar symptoms to other types of Leigh syndrome. The age of onset is, on average, 5 months and the median age of death is 1 year and 7 months. Children with the disease are developmentally delayed, have mildly dysmorphic facial features, including hypoplasia of the midface and wide nasal bridge, chronic metabolic acidosis, and hypotonia (decreased muscular strength). Other symptoms include tachypnea (unusually quick breathing rate), poor sucking ability, hypoglycemia (low blood sugar), and tremors. Severe, sudden metabolic acidosis is a common cause of mortality.