Symptoms of Leigh syndrome usually progress rapidly. Since the disease affects central nervous system, initial signs of leigh syndrome may include, poor sucking ability, loss of head control and motor functions.
Loss of appetite, irritability, continuous crying (in infants), vomiting, and seizures may sometimes accompany these symptoms. As leigh syndrome becomes worse, symptoms may also include:
- Generalized weakness
- Heart problems
- Low muscle tone (hypotonia)
- Breathing difficulty
- Episodes of lactic acidosis (accumulation of lactic acid in the body and brain) which may impair respiratory and kidney function
Life expectancy is usually around a year within the onset of symptoms, although both acute disease of a few days and prolonged survival have been reported.
The sufferers usually do not live long after contracting leigh syndrome. Only few children suffer from leigh syndrome can survive until their teens. If the disease affects individuals in their early adulthood, then the progression of the disease is slightly slow compared with other patients.