Table 2b.

Mitochondrial DNA Maintenance Defects Presenting with Encephalomyopathy

GeneDisorderMOImtDNA
Maintenance
Defect		Usual Age
of Onset		Common Manifestations in
Addition to Muscle Weakness
ABAT Encephalomyopathy w/elevated GABA (OMIM 613163)ARDepletionInfancy
  • DD
  • Hypotonia
  • Epilepsy
  • ↑ GABA in plasma, urine, & CSF
FBXL4 Encephalomyopathic mtDNA depletion syndrome ARDepletionNeonatal
or infancy
  • DD
  • Hypotonia
  • Epilepsy
  • Hearing impairment
  • Lactic acidosis
OPA1 Encephalomyopathy
(OMIM 616896)		ARDepletionInfancy
  • DD
  • HCM
  • Optic atrophy
POLG Myoclonic epilepsy-myopathy-sensory ataxia ARMultiple deletionsEarly
adulthood
  • Epilepsy
  • Ataxia
RNASEH1 Encephalomyopathy
(OMIM 616479)		ARDepletion & multiple deletionsEarly
adulthood
  • Ophthalmoplegia
  • Ptosis
  • Ataxia
RRM2B Encephalomyopathy w/renal tubulopathy ARDepletionNeonatal
or infancy
  • DD
  • Hypotonia
  • GI dysmotility
  • Renal tubulopathy
SUCLA2 Mitochondrial DNA depletion syndrome, encephalomyopathic form w/methylmalonic aciduria ARDepletionInfancy
or early
childhood
  • DD
  • Hypotonia
  • Dystonia
  • Hearing impairment
  • ↑ methylmalonic acid
SUCLG1 Mitochondrial DNA depletion syndrome, encephalomyopathic form w/methylmalonic aciduria ARDepletionNeonatal
or infancy
  • DD
  • Hypotonia
  • Hearing impairment
  • ↑ methylmalonic acid

AR = autosomal recessive; CSF = cerebrospinal fluid; DD = developmental delay; GI = gastrointestinal; MOI = mode of inheritance; mtDNA = mitochondrial DNA

From: Mitochondrial DNA Maintenance Defects Overview

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