We report a patient with
mitochondrial encephalomyopathy presenting
parkinsonism, as well as her brother who had
ataxia but not
parkinsonism. Both patients had
myopathy,
deafness, and
insulin-dependent diabetes mellitus. The proband was a 55-year-old woman, who has developed progressive difficulty in walking and slowness of movement since 53 years of age, becoming bed-ridden at 55. Neurological examination revealed mental impairment, a masked face, Myerson's sign, vertical supranuclear
ophthalmoplegia, and severe sensorineural
deafness,
hypokinesia, rigidospasticity, and weakness of the extremities. But
tremor and
cerebellar ataxia were absent. Her 48-year-old brother gradually developed weakness of the lower extremities and drunken gait over a few years. On neurologic examination, vertical supranuclear
ophthalmoplegia, moderate sensorineural
deafness, and
cerebellar ataxia were present, but
parkinsonism was absent. Three other siblings were reported to have died in early childhood. Cranial MR imaging showed cerebral
atrophy and mild
atrophy of the cerebellar vermis as well as mild periventricular hyperintensities in T2-weighted images in both patients. However, no
infarcts were seen. Laboratory investigations revealed slightly elevated
lactate and
pyruvate levels in the proband and elevation of
pyruvate in her brother. A biopsy specimen obtained from the quadriceps muscle showed ragged-red fibers with modified Gomori trichrome staining, and a decrease of complex I+III and complex II+III activity in the proband.
Mitochondrial DNA (
mtDNA) analysis using the polymerase chain reaction and restriction
enzyme Apa I showed a point mutation in the
tRNA(Leu)(UUR)) gene (an A to G transition at
nucleotide 3243) in both patients.(ABSTRACT TRUNCATED AT 250 WORDS)