HLA-B27 defects (for want of a better word) can cause either or both:
- haemochromotosis (iron accumulation - just monitor iron levels to track this)
- inflammation (ankylosing spondylitis, iritis and IBS are some of the most commonly reported).
But having the defect doesn't necessarily cause problems. So you need a bit more information.
What is the exact defect? Which genes? What are the symptoms?
There are three genes (or SNPs? I don't know what to call them), and everyone has two copies of each one.
For example, my husband is homozygous for one of the less problematic genes, so he shouldn't have issues according to the doctor, but he still needs to give blood once a year. But his brother has the same genes, and he has ankylosing spondylitis, iritis and more. My husband can eat anything he wants, his brother needs to severely restrict starches. My son is heterozygous for one gene (no prizes for guessing which parent donated that one!) and he is not affected at all from it.
Other people we know are homozygous for the 'bad' gene and they have to give blood every three months, and the blood gets thrown away because it is unusable for anyone else.
So being told you 'have' hla-b27 might be bad, a minor nuisance, or indifferent.
Doctor advice can be variable. Some try to tell you it doesn't matter at all - they haven't yet caught up with discovery of the gene back in the mid-1990s. Others try to tell you that even being heterozygous is a cause for concern. Some doctors denounce any form of dietary advice, others give too much weight to diet. It's like CFS - it's so individual and you need to try for yourself.
EDIT: I don't know anything about that other FUT2 gene variant thing. Sorry.