AH amyloidosis associated with lymphoplasmacytic lymphoma secreting a monoclonal γ heavy chain carrying an unusual truncated D segment

To date, the presence of amyloidosis associated with immunoglobulin heavy chain (AH amyloidosis) was reported in only 7 cases. Although AH amyloidosis is caused mainly by plasma cell dyscrasia, as in AL amyloidosis, we report a 61-year-old patient who presented with nephrotic syndrome caused by AH amyloidosis associated with lymphoplasmacytic lymphoma. Biochemical and molecular analyses of the deposited amyloid fibrils and heavy-chain genes of lymphocytes showed that proliferative lymphoma cells produced a gamma heavy chain, not a mu heavy chain, which carried an unusual truncated diversity (D) segment of the variable region. Our results indicate that production of the abnormal heavy chain caused by the partially deleted D segment gene is responsible for gamma heavy-chain-related amyloid fibril formation in this patient.