This post is from Dierdre Menyo on the mma list- 

Hi all,

This question often comes up.  MM  can change from secreting  
immunoglobulin (i.e., IgG or IgA) to free light chains only.   
Evidently these authors attribute this kind of switch to the new  
drugs.  (Or so it seems to me.)

Reproduced here under fair use of copyright doctrine: for  
educational, non-profit purposes.

Haematologica, Vol 92, Issue 1, 143-144

Multiple Myeloma
Extramedullary relapse of multiple myeloma associated with a shift in  
secretion from intact immunoglobulin to light chains
Mark A. Dawson*,, Sushrut Patil?, Andrew Spencer*,?

* Department of Haematology and Bone Marrow Transplantation, The  
Alfred Hospital, Commercial Road, Prahran, Melbourne, Victoria 3181,  
Australia;
? Department of Clinical Haematology, Monash Hospital, Clayton Road,  
Clayton, Melbourne, Victoria 3168, Australi

Correspondence: Mark A. Dawson, The Alfred, Commercial Road, Prahran,  
Melbourne, Victoria, Australia 3181. Phone: international  
+61.39.2762000. Fax: international + 61.39.2763021. E-mail:  
dawsonm@ausdoctors.net

Biological therapies in multiple myeloma have heralded a new and  
exciting era for treatment to combat this disease. However the  
evolutionary pressures that these drugs place on the microenvironment  
has resulted in a change in the biological behaviour of this  
malignancy and novel manifestations of relapsed disease. This is  
illustrated in our series of three patients showing fulminant relapse  
of disease with plasmablastic features, an extramedullary  
predilection and a shift in secretion from intact immunoglobulin to  
free light chains only.

Best wishes,

Deirdre