Following normal early development until one year old, weakness appears and worsens rapidly, causing respiratory failure and death typically within a few years.

Neonatal weakness, hypotonia requiring assisted ventilation, possible renal dysfunction. Severe lactic acidosis. Prominent ragged-red fibers. Death due to respiratory failure usually occurs prior to one year of age.

Enlarged liver and intractable liver failure, myopathy. Severe lactic acidosis. Death is typical within the first year.