I personally never heard of it but below is a link that can maybe help you better understand.
If it involves insufficient vitamin B12 I do know this can be a trigger to AHUS.
Hope this helps
My name is Tara and I have been working to identify genetic causes that lead to aHUS for my PhD thesis for the past 5 years in Dr. Richard Smith's Lab. Linda Burke sent me a message about whether or not I know anything about (or am working on) MTHFR in our lab.
So the quick answer is I have not heard of aHUS patients having variants that cause disease in this gene. Thus far we only know of a few genes that lead to aHUS when they are not working correctly. These include: CFH, CFI, MCP, CFB, C3, and THBD. Other things that are known to lead to aHUS are deletions in the CFHR genes (CFHR1-5) as well as anti-FH autoantibodies. When these variants are present they lead your alternative pathway (part of the complement cascade) to be overactive and attack your body’s healthy cells.
That is what we do know. Now to answer your question on what the variant in MTHFR may mean. I can’t say for sure. While I have never heard of mutations in this gene being a cause of aHUS I do know that common polymorphisms (changes in the DNA) in MTHFR can predispose to excessive clotting among other problems. If you are interested in this here is an informative link (including the connection between it and B12 levels):
The gene itself starts the conversion of 5, 10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine. When it does not work this can lead to an increased amount of the chemical homocysteine in the blood, and when there is an excess of homocysteine this increases clotting. aHUS is a rare clotting disease which may be why your doctor ordered genetic testing of MTHFR, especially if testing of the other 6 genes was negative.
I found one reported case of two sisters each with the same homozygous (two copies of the nonworking gene) mutation in MTHFR. They were diagnosed at first with HUS (not aHUS), then cblC disease. One of the sisters also had a mutation in CFH and this sister had the more severe case. Here is a link to the paper:
However, in another study they found that the three common inherited thrombophilia factors (factor V, F5 c.1691G > A; methylenetetrahydrofolate reductase, MTHFR c.677 C > T and prothrombin, F2 c.20210 G > A) were not susceptibility factors for the development of aHUS.
So while it is possible that the mutation found in your case is involved in aHUS at this point to my knowledge not enough is known about it to tell you what to expect. I also don’t know what the mutation was that was found so I can’t be specific about what it may mean. This is one of frustrating things about genetic testing. We can test for mutations but then when it’s something we’ve never seen before we have to be careful about saying whether or not the mutation is disease causing. It could just be one of the thousands of non-disease causing changes that we all have in our DNA. This is why further functional studies are typically done.
I hope this is helpful. However, I am not an MD so there may be something different about your case which is why your doctor ordered this test. If you have any other questions let me know and if I can I will try and answer them.