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IEMbase 0150: RRM2B-related mitochondrial DNA depletion syndrome 8

Scope

Field Value
IEMbase ID 150
Nosology 9.1.07.01
Gene RRM2B
External IDs OMIM:604712; ORPHA:298
Generated mapping UNMAPPED
Candidate DisMech targets Partial local context in Mitochondrial_Neurogastrointestinal_Encephalomyopathy.yaml#MNGIE-like RRM2B
Review date 2026-07-07

IEMbase phenotype signal

IEMbase represents this as RRM2B-related mitochondrial ribonucleotide reductase subunit 2 deficiency, with alternate label mitochondrial DNA depletion syndrome 8A and 8B. Treatability is marked unknown.

The biochemical rows include increased plasma and CSF lactate, decreased muscle cytochrome C oxidase, and increased histochemical mitochondrial proliferation. Clinical rows include muscle mitochondrial DNA depletion, encephalomyopathy, gastrointestinal dysmotility, hearing loss, hypotonia, peripheral neuropathy, ophthalmoplegia, renal tubulopathy, and perinatal death.

DisMech phenotype coverage

The generated table leaves this unmapped, but local partial coverage exists in Mitochondrial_Neurogastrointestinal_Encephalomyopathy.yaml, which includes a MNGIE-like RRM2B subtype. That subtype records RRM2B as a rare MNGIE-type gene and covers overlapping gastrointestinal dysmotility, ophthalmoplegia, and peripheral neuropathy context.

The local MNGIE entry is still anchored on classic TYMP-related MNGIE. It does not serve as a full standalone target for RRM2B mitochondrial DNA depletion syndrome 8A/8B, especially for the perinatal, renal tubulopathy, lactate, cytochrome C oxidase, and mtDNA-depletion details in IEMbase.

Concordance and completeness

Judgement: partial false negative; local subtype context exists but no canonical MTDPS8A/8B target.

RRM2B is present locally, so this should not be treated as complete absence of coverage. But mapping the IEMbase record directly to classic MNGIE would also be too broad, because IEMbase is focused on RRM2B mitochondrial depletion syndrome rather than TYMP thymidine phosphorylase deficiency.

Curation actions

  • Record Mitochondrial_Neurogastrointestinal_Encephalomyopathy.yaml#MNGIE-like RRM2B as partial context, not an exact standalone mapping.
  • Future curation should add or split a RRM2B/MTDPS8A-8B target with mtDNA depletion, lactic acidosis, COX deficiency, encephalomyopathy, renal tubulopathy, hearing loss, ophthalmoplegia, GI dysmotility, and perinatal lethality.