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Point mutation tRNA(Ser(UCN)) in a child with hearing loss and myoclonus epilepsy

Gian Paolo Ramelli1, Sabina Gallati, Joachim Weis

  • 1Department of Pediatrics, Ospedale San Giovanni, Bellinzona, Switzerland. gianpaolo.ramelli@eoc.ch

Journal of Child Neurology
|August 12, 2006
PubMed

Insights

Maternally inherited mitochondrial disorder causes sensorineural hearing loss, myoclonus epilepsy, and diabetes. Treatment with ubiquinone and vitamin C improved psychomotor development in a patient with a novel mitochondrial DNA mutation.

Area of Science:

  • Genetics
  • Neurology
  • Biochemistry

Background:

  • Mitochondrial disorders can present with a wide range of symptoms due to impaired energy production.
  • Maternally inherited conditions are passed down through the mitochondrial DNA (mtDNA).

Observation:

  • A family presented with a syndrome including sensorineural hearing loss, myoclonus epilepsy, ataxia, psychomotor retardation, short stature, and diabetes mellitus.
  • The affected 12-year-old boy exhibited progressive neurological and developmental decline.
  • Muscle biopsy and blood/CSF lactate/pyruvate levels were normal, complicating diagnosis.

Findings:

  • Biochemical analysis revealed decreased activity of respiratory chain complexes I and IV.
  • Sequence analysis identified a homoplasmic T-to-C substitution at np 7512 in the mitochondrial tRNA(ser(UCN)) gene.
  • Asymptomatic maternal relatives were heteroplasmic for this mutation.

Implications:

  • This finding suggests a novel mtDNA mutation associated with a complex mitochondrial syndrome.
  • mtDNA analysis is recommended for patients with hearing loss and myoclonus epilepsy, even without typical biochemical markers.
  • Combined ubiquinone and antioxidant therapy may offer therapeutic benefits for such conditions.

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