Q. Why do light chains appear in the urine in mu heavy chain disease but not in alpha or gamma heavy chain diseases?
A. Heavy chain diseases (HCDs) are B-cell proliferations in which the cells produce abnormal immunoglobulin heavy chains. The cells can produce any type of heavy chain they want except IgE (at least it’s never been described).
Alpha HCD, in which the B cells produce heavy chains resembling those of IgA molecules, is the most common HCD (HCD itself being pretty uncommon). It tends to occur in younger patients; many are in their 30s. Gamma HCD, also called Franklin disease after the first person to report the disease, frequently occurs in association with autoimmune disorders like rheumatoid arthritis and lupus. The prognosis is not so great, with survival on the order of months to a few years. Mu chain disease is very rare, and the prognosis is more variable, on the order of months to many years.
As far as your question goes: you’re right: you can see light chains in the urine of patients with mu HCD, but you don’t see them in patients with alpha or gamma HCD. In mu HCD, the B cells produce light chains, but they can’t be attached to the mu heavy chains because there are abnormalities in the mu chains that prevent the assembling of complete Ig molecules. So – the light chains that are formed are free to be filtered into the urine.  In alpha and gamma HCD, you don’t see light chains in the urine because the B-cells in these disorders only make heavy chains – no light chains at all.
any specific symptom regarding HCD
Actually, there is at least one case of gamma HCD with free light chains in urine (Lopez-Anglada, 2010). The reason why light chains are not produced by neoplastic B cells in almost all gamma and alpha HCD is probably related to the hypermutation process, which might be activated at such a level that stop codons would prevent production of light chains.
Great – thanks for the details!
Just wanted to chime in as I have Gamma heavy chain disease. The prognosis may be bad but, I was diagnosed in april of 08 and after doing no treatment I am feeling good and l. nodes are returning to normal size, also blood counts have rebounded, go figure. Male 47 yrs
Wonderful!! Thanks for sharing your story. Best wishes – sounds like you’re doing great.
I’ve got GHC. I do’nt know what’s in store. Is Chop therapy the only solution for recovery. I’m experiencing just sweats daily and low grade fevers, but in general i feel great.