[koontzkg]

Difference between multiple myeloma & AL amyloidosis?

by koontzkg on Tue Oct 28, 2014 10:33 am

What is the difference between multiple myeloma and AL amyloidosis? What are the hallmarks that makes one a cancer and one not – aggressiveness of disease, genetic mutations that allow overpopulation of cells? Doesn't AL mutate over time, developing resistance to therapies? Why is a myeloma plasma cell considered malignant and an amyloidosis plasma cell not?

I have AL amyloidosis but don't meet the old or new criteria for multiple myeloma. I know that many multiple myeloma patients also have AL, but that's not the situation I'm wondering about. It's for those who have AL but not multiple myeloma.

I understand the difference in diagnosis, prognosis, disease progression and treatment. I guess you'd say I was wondering more about pathogenesis and pathological features.

Thanks,
Kathy

[Dr. Prashant Kapoor]

Re: Difference between multiple myeloma & AL amyloidosis?

by Dr. Prashant Kapoor on Thu Oct 30, 2014 11:44 pm

While myeloma and AL amyloidosis are both monoclonal plasma cell disorders and treated in a somewhat similar fashion, there are significant differences between these two diseases.

Although the proportion of abnormal plasma cells is generally small in AL amyloidosis as compared to myeloma, the plasma cells producing light chains in AL amyloidosis frequently act as "dangerous B cell clones." A clone is a population of cells with identical features that are derived from the same ancestral cell. The morbidity and mortality in amyloidosis is from misfolding of light chains that deposit in the form of amyloid material in various organs and compromise their functions.

The terms 'malignant ' or 'non-malignant' are not very accurate descriptors since in both multiple myeloma and AL amyloidosis the growth of plasma cells is uncontrolled. Both diseases cause end organ damage, but different mechanisms are involved. For example, in myeloma, there is direct destruction of bones and damage to the kidneys when free light chains clog the kidney tubules (cast nephropathy).

While kidney damage is also evident in AL amyloidosis, the mechanism of damage is different. In AL amyloidosis, the free light chains can deposit in the glomeruli (filtering units) of the kidney, rendering them leaky and malfunctional. Like myeloma cells, AL cells can also mutate over time and become resistant to therapies.

Hope this explanation clarifies some of your doubts.

[koontzkg]

Re: Difference between multiple myeloma & AL amyloidosis?

by koontzkg on Fri Oct 31, 2014 9:31 am

Thanks for the info, Dr. Kapoor. One thing I still don't quite understand is why multiple myeloma is considered a cancer and AL amyloidosis is not. Is there an easy to understand explanation for that?

[AliceNorth]

Re: Difference between multiple myeloma & AL amyloidosis?

by AliceNorth on Fri Oct 31, 2014 11:49 am

I agree, Kathy. If the plasma cells in both AL amyloidosis and myeloma multiply uncontrollably and both become resistant to treatment, what is the defining factor that makes myeloma a cancer?

Under the new guidelines, I do not have myeloma, but I was diagnosed with myeloma to­geth­er with amyloidosis. If it is correct that I technically do not have cancer, does this improve my prog­nosis? I'm not sure it does.

[Dr. James Hoffman]

Re: Difference between multiple myeloma & AL amyloidosis?

by Dr. James Hoffman on Fri Oct 31, 2014 3:10 pm

In a (somewhat over-simplified) way, the blood disorder underlying AL amyloidosis can be con­sidered a monoclonal gammopathy of undetermined significance (MGUS). It has, how­ever, the unfortunate additional characteristic that the light chains it produces can misfold into amyloid and cause organ damage. So, as a plasma cell disease, it has benign character­istics, but as an illness, it can make people very sick.

As far as I am concerned, you can call AL amyloidosis a cancer if needed (e.g., to be eligible for a cancer insurance policy, or some other cancer related benefits). As Dr. Kapoor implied, the terminology malignant vs. not malignant is open to interpretation.

Hope this adds a bit.

[koontzkg]

Re: Difference between multiple myeloma & AL amyloidosis?

by koontzkg on Fri Oct 31, 2014 4:59 pm

Thanks Dr. Hoffman! The MGUS reference helps. The way I frame it up in my mind is that it's because the only mechanism of injury is due to a secondary product of the plasma cell clone (the amyloids), not directly from the clone. Hope I'm right.

[koontzkg]

Re: Difference between multiple myeloma & AL amyloidosis?

by koontzkg on Mon Nov 03, 2014 1:58 pm

I thought about the comment that AL Amyloidosis is an MGUS. For those of us with it, I think its significance is pretty well determined.