Leigh syndrome, French-Canadian type (LSFC), is a subtype of Leigh syndrome, and is a severe neurologic disorder caused by the deficiency of the enzyme COX. This condition is characterized by progressive loss of mental and movement abilities starting in the first year of life. Symptoms include low muscle tone, difficulty coordinating movement, and development of tissue damage in the brain. A distinctive facial appearance is present at birth. Affected individuals tend to have episodic crises triggered by severe illness or infections in early childhood where symptoms may worsen and are accompanied by difficulty breathing, seizures, coma, and often lead to early death. Some individuals survive into early childhood but typically have intellectual disability. There is no cure for LSFC; however medical surveillance and care may help to improve some symptoms and overall condition of life. This disease is caused by pathogenic variants in LRPPRC gene.