A group of mitochondrial DNA maintenance syndrome diseases with characteristics of predominantly neuromuscular manifestations with typically infantile onset of hypotonia, lactic acidosis, psychomotor delay, progressive hyperkinetic-dystonic movement disorders, external ophthalmoplegia, sensorineural hearing loss, seizures and variable renal tubular dysfunction. It may be associated with a broad range of other clinical features. [from
SNOMEDCT_US]