Yes, it’s incredibly tricky trying to avoid environmental contaminants, and there’s also individual susceptibility (so my haematologist says) which is also a factor.
I think having different light chains expressed is less significant than the fact you’re both IgA, insofar as the light chains are secondary to the fact you both had a rarer type of monoclonal production. Having said that, sadly it’s been investigated that lambda increases risk, whereas for you kappa is a lesser risk ❤️‍🩹
https://ashpublications.org/blood/article/130/Supplement%201/1780/79509/High-Risk-Myeloma-Is-Demarcated-By-Immunoglobulin
I’ve had considerable exposure to toxins as a kid and young adult, which may be what’s contributed to the development of MGUS? I know I was showing elevated proteins back 7 years ago now (when I was 43), which was unexpected for my gender/ethnicity, however the doc was hesitant to send me to haematology - and didn’t do so - for another 5 years, and it was 2 years ago a BMB showed IgG lambda. This is when I learned what this problem was called, and subsequently was able to undertake research. I had the second BMB today, because the new haematologist thinks I have amyloidosis/light chain deposition disease due to recent increases in Lambda/outside normal K:L ratio, and kidney disease, along with fibrosis in lungs and developing premature ventricular contractions (something I find very uncomfortable because an hour or so of this gives rise to feeling very weak with chest discomfort - very disruptive to sleep when it happens at night). I also have brain inflammation and peripheral neuropathy, so she’s hoping this BMB can give us some answers, along with a kidney biopsy early December. She also thinks I might have a condition called CVID (common variable immunodeficiency), because of a history of bad infections from childhood. The treatment for that is SCIg (subcutaneous immunoglobulin) from those lovely people whom donate blood (it’s a donor product), but that will not have an impact on MGUS/SMM, it will only help with increasing immunity against infection (I’m currently on two consecutive antibiotics for the last few months because I can’t shake an infection, so this may indeed help that underlying problem..the immunologist explained it as IgG has a few different subtypes, called IgG1, IgG2, etc, and I have significantly low IgG1, which apparently is associated with CVID. Then, having bad lambda that aren’t formed properly, they don’t ‘see’ the invaders, and pretty much ignore infections. So the test is, I go have a pneumococcal vaccine and then 6-8 weeks later see if I have a positive serum response: if not, I have CVID, if I have antibodies to the vaccine, then the low immunity is related to MGUS/SMM - especially with low IgA, which was found in the BMB 2 years ago). Anyway, I digress, however I thought it might be interesting to see the intersection of potential inherited or acquired (CVID can be both) concomitant immune deficiency, and the question of how these types of things can coexist, and maybe contribute to symptomatology 🙂

My husband was diagnosed end 2021 and I was diagnosed last week. He had a stroke early last year and, as I now know, we didn't ask enough questions about his diagnosis. We do not know which type he has and I have not had an opportunity to talk to anyone about my diagnosis, just got a letter! We are in the UK. AS you say I wish I knew what did this to us so I could avoid it or at least tell others about it, whatever "it" is.

Hi there, thank you for your post. Just out of curiosity, did you and Steve both get the COVID vaccine?