Table 2.

Phenotypic Spectrum of RRM2B Mitochondrial DNA Maintenance Defects

Relative PrevalencePhenotypeMOIOnsetCommentsDisease Pathogenesis
CommonRRM2B encephalo-
myopathic MDMD		ARInfancySevere multisystem disease often fatal in early lifemtDNA depletion
adPEO 1ADAdulthoodMilder & often tissue-specificClonally expanded (multiple) mtDNA deletions 2
RareMNGIE 3ARChildhood or adulthoodGI dysmotility, PEO, ptosis, peripheral neuropathy & leukoencephalopathymtDNA depletion
arPEO 1AREarly childhood or adulthoodMultisystem involvement & Kearns-Sayre syndrome-like 4Clonally expanded (multiple) mtDNA deletions 2

AD = autosomal dominant; AR = autosomal recessive; GI = gastrointestinal; MDMD = mitochondrial DNA maintenance defects; MOI = mode of inheritance; MNGIE = mitochondrial neurogastrointestinal encephalopathy; PEO = progressive external ophthalmoplegia

1.

For review of the adPEO and arPEO phenotypes, see POLG-Related Disorders.

2.

Accumulation of clonally expanded (multiple) mtDNA deletions causes tissue-specific cytochrome c oxidase (COX) deficiency.

3.
4.

For review of the Kearns-Sayre syndrome phenotype, see Mitochondrial DNA Deletion Syndromes.

From: RRM2B Mitochondrial DNA Maintenance Defects

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