Syndrome caused by impairment of mitochondria. Whilst mitochondrial disorders may be caused by impairment of a single stage of energy production, individuals with multiple mitochondrial dysfunctions syndrome have reduced function of more than one stage. Symptoms begin in early life and affected individuals usually do not live past infancy. Symptoms include encephalopathy, hypotonia, seizures and psychomotor delay. Most affected babies have lactic acidosis that can be life threatening.