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Multiple presentation of mitochondrial disorders


The aim of this study was to assess the heterogeneous clinical presentations of children with mitochondrial disorders evaluated at a metabolic neurogenetic clinic. The charts of 36 children with highly suspected mitochondrial disorders were reviewed. Thirty one children were diagnosed as having a mitochondrial disorder, based on a suggestive clinical presentation and at least one of the accepted laboratory criteria; however, in five children with no laboratory criteria the diagnosis remained probable. All of the patients had nervous system involvement. Twenty seven patients also had dysfunction of other systems: sensory organs in 15 patients, cardiovascular system in five, gastrointestinal system in 20, urinary system in four, haematopoietic system in four, and endocrine system in nine. The clinical presentation was compatible with an established syndrome in only 15 children. Severe lactic acidosis or ragged red muscle fibres were encountered in very few patients. These results suggest that mitochondrial disorders should be evaluated in children presenting with a complex neurological picture or multisystem involvement.

  • A full mitochondrial evaluation is warranted in children with a complex neurological picture or a single neurological symptom and other system involvement

  • When the presentation is classic for a maternally inherited mitochondrial syndrome—for example, mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), myoclonic epilepsy and ragged red muscle fibres (MERRF), Leber’s hereditary optic neuropathy (LHON), appropriate mitochondrial DNA studies should be obtained first

  • When the clinical picture is classic for a nuclear DNA inherited syndrome and the gene or the linkage is known—for example, MNGIE (mitochondrial neurogastrointestinal encephalopathy) or DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness), proceed with genetic studies

  • When the clinical picture is non-specific but highly suggestive of a mitochondrial disorder, start with serum and/or cerebrospinal fluid lactic acid and urinary organic acids and proceed with muscle biopsy and assessment of the respiratory chain enzymes

  • Normal serum or cerebrospinal fluid lactic acid does not exclude a mitochondrial disorder

  • mitochondrial disorders
  • mitochondrial DNA
  • respiratory chain
  • pyruvate dehydrogenase

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