 These mitochondrial effects are responsible for the symptomatology associated with the disease.While the disease manifests early in life in most cases, diagnosis of the disease is often quite delayed.The symptoms that affected patients present vary, but the most common presenting symptoms are gastrointestinal issues such as nausea, vomiting, abdominal pain, and diarrhea, and neurologic or ocular symptoms such as hearing loss, weakness, and peripheral neuropathy.