Genetic testing: variable single mtDNA (mitochondrial DNA) deletions
Onset: before age 20
Clinical features:
(1) pigmentary retinopathy (retinitis pigmentosa)
(2) progressive external ophthalmoplegia (PEO)
(3) cerebellar ataxia
(4) leukoencephalopathy with intellectual disability and/or dementia
(5) sensorineural hearing loss
(6) ptosis
(7) oropharyngeal dysfunction
(8) esophageal dysfunction
(9) myopathy with muscle weakness and exercise intolerance
(10) cardiac conduction block
(11) cardiomyopathy
(12) endocrinopathy (diabetes mellitus, hypoparathyroidism, hypothyroidism, adrenal insufficiency)
(13) pancreatic exocrine failure
(14) short stature
(15) renal dysfunction
Laboratory findings:
(1) elevated serum lactate and pyruvate
(2) elevated CSF protein (> 1 g/L)
