Multiple myeloma and amyloid bone lesions complicating rheumatoid arthritis.

Multiple myeloma developed in a woman with a 7-year history of seropositive rheumatoid arthritis (RA). An unexpected finding was the presence of massive amyloid deposits in the left femur and traces of amyloid in the synovium. Detailed histopathologic studies, however, conclusively excluded amyloid arthropathy. Although definitive tissue classification was not possible, this patient in all likelihood had 2 types of amyloid: massive bone lesions of myeloma-associated (AL) amyloid, and focal subsynovial deposits of RA-associated secondary (AA) amyloid.