nandixon
Senior Member
- Messages
- 1,092
I think @Freddd almost certainly has a late-onset cobalamin deficiency type C (cblC) defect. So he probably has one or more significant mutations on the MMACHC gene. @richvank mentioned this several times before his passing.
Unfortunatey, there are several hundred SNPs on that gene, and several dozen mutations on it have been found that cause cblC deficiency. 23andMe only tests for a handful (9 on the v3 chip, maybe less on the current v4 version), so he'd need to have that gene sequenced.
I'm sure a research institution would be willing (and happy) to do this. He might want to see a genetics counselor who could act as a liaison. I did something similar several years ago with an unrelated mutation that I have.
A cblC defect easily explains all of his symptoms and various reactions to different supplements, for example: why he can't use cyanocobalamin; why he needs such large amounts of both methylcobalamin and adenosylcobalamin; why taking glutathione and N-acetylcysteine supplements cause excessive excretion of his B12, etc.
Here are just a few of many references on this:
Cobalamin C defect: natural history, pathophysiology, and treatment
http://www.ncbi.nlm.nih.gov/pubmed/20632110/
Three new cases of late-onset cblC defect and review of the literature illustrating when to consider inborn errors of metabolism beyond infancy
http://www.ncbi.nlm.nih.gov/pubmed/25398587/
Spectrum of mutations in MMACHC, allelic expression, and evidence for genotype-phenotype correlations
http://www.ncbi.nlm.nih.gov/pubmed/19370762/
Glutathione metabolism in cobalamin deficiency type C (cblC)
http://www.ncbi.nlm.nih.gov/pubmed/23568438/
Protection of aquo/hydroxocobalamin from reduced glutathione by a B12 trafficking chaperone
http://www.ncbi.nlm.nih.gov/pubmed/21429294/
Unfortunatey, there are several hundred SNPs on that gene, and several dozen mutations on it have been found that cause cblC deficiency. 23andMe only tests for a handful (9 on the v3 chip, maybe less on the current v4 version), so he'd need to have that gene sequenced.
I'm sure a research institution would be willing (and happy) to do this. He might want to see a genetics counselor who could act as a liaison. I did something similar several years ago with an unrelated mutation that I have.
A cblC defect easily explains all of his symptoms and various reactions to different supplements, for example: why he can't use cyanocobalamin; why he needs such large amounts of both methylcobalamin and adenosylcobalamin; why taking glutathione and N-acetylcysteine supplements cause excessive excretion of his B12, etc.
Here are just a few of many references on this:
Cobalamin C defect: natural history, pathophysiology, and treatment
http://www.ncbi.nlm.nih.gov/pubmed/20632110/
Three new cases of late-onset cblC defect and review of the literature illustrating when to consider inborn errors of metabolism beyond infancy
http://www.ncbi.nlm.nih.gov/pubmed/25398587/
Spectrum of mutations in MMACHC, allelic expression, and evidence for genotype-phenotype correlations
http://www.ncbi.nlm.nih.gov/pubmed/19370762/
Glutathione metabolism in cobalamin deficiency type C (cblC)
http://www.ncbi.nlm.nih.gov/pubmed/23568438/
Protection of aquo/hydroxocobalamin from reduced glutathione by a B12 trafficking chaperone
http://www.ncbi.nlm.nih.gov/pubmed/21429294/
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