Methylmalonic Aciduria and Homocystinuria, cobalamin C (cblC) Type

Methylmalonic aciduria and homocystinuria, cblC type, is a defect in B12 metabolism. Patients may present with severe early-onset disease that includes megaloblastic and macrocytic anemia, failure to thrive, microcephaly, lethargy, and feeding difficulties. Neurologic symptoms may include seizures, hypotonia, intellectual disability, developmental delay, ataxia, optic atrophy, retinal degeneration, and pigmentary retinopathy. Late-onset cases may present with megaloblastic anemia and/or psychiatric disturbance, anorexia, irritability, fatigue, myelopathy, nephropathy, thromboembolic events, or dementia.

Tests Available

Forms and Documents

Test Details

  • Confirmation of a biochemical/clinical diagnosis
  • Carrier testing
  • Prenatal diagnosis in at risk pregnancies


3-4 weeks
2-5 mL Blood - Lavender Top Tube
Buccal Swabs

*Reporting times are typical, but could be extended in situations outside GeneDx's reasonable control.


  • 270.4 Disturbances of sulphur-bearing amino-acid metabolism, Cystathioninemia, Cystathioninuria, Disturbances of metabolism of methionine, homocystine, and cystathionine Homocystinuria, Hypermethioninemia, Methioninemia
  • 270.9 Unspecified disorder of amino-acid metabolism
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**The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.


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  7. Stucki et al. (2012) Human Molecular Genetics 21 (6):1410-8 (PMID: 22156578)
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