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IEMbase 0744: MT-CYB-related mitochondrial cytochrome b deficiency

Scope

Field Value
IEMbase ID 744
Nosology 6.1.01.02
Nosology code IEM0487
Gene MT-CYB
External IDs OMIM:516020; ORPHA:1460
Generated mapping UNMAPPED; weak candidate 3-Hydroxy-3-Methylglutaryl-CoA_Synthase_Deficiency.yaml
Candidate DisMech targets No exact MT-CYB / mitochondrial cytochrome b target identified
Review date 2026-07-07

IEMbase phenotype signal

IEMbase represents mitochondrial MT-CYB-related cytochrome b deficiency, an mtDNA-encoded complex III disease. The cached rows are broad: low free carnitine, normal-to-high transaminases and creatine kinase, urinary 3-methylglutaconic acid, CSF/MRS/plasma/urine lactate elevations, adult ataxia, possible adult cardiomyopathy, cataract, sensorineural deafness, episodic encephalopathy, ophthalmoplegia, psychiatric disturbance, visual impairment, childhood cognitive impairment, possible hypoglycemia, childhood possible stroke-like episodes, adult hypotonia and muscle cramps, weight loss across childhood to adulthood, possible brainstem/cerebellar/cortical atrophy, marked exercise intolerance, gastrointestinal dysmotility, proximal muscle weakness, polyneuropathy, and seizures.

DisMech phenotype coverage

No exact MT-CYB local target was identified.

The generated 3-Hydroxy-3-Methylglutaryl-CoA_Synthase_Deficiency.yaml candidate is unrelated to the disease identity and should be rejected. Current DisMech content includes mitochondrial and respiratory-chain context, but no dedicated mtDNA cytochrome b / complex III entry.

Concordance and completeness

Judgement: true MT-CYB complex III local gap.

IEMbase is strong for phenotype seeding: it captures multi-compartment lactate, organic-acid and enzyme-test abnormalities, exercise intolerance, myopathy, neuropathy, neuroimaging, episodic encephalopathy, seizures, ocular/auditory features, gastrointestinal dysmotility, weight loss, and possible cardiomyopathy or stroke-like episodes. DisMech lacks the core MT-CYB disease entity.

Curation actions

  • Add a dedicated MT-CYB mitochondrial cytochrome b / complex III deficiency target if curated.
  • Reject 3-Hydroxy-3-Methylglutaryl-CoA_Synthase_Deficiency.yaml as exact coverage.
  • Preserve lactate, 3-methylglutaconic acid, CK/transaminases, exercise intolerance, proximal weakness, neuropathy, seizures, neuroimaging, ocular/auditory, gastrointestinal, and cardiomyopathy prompts.