Molecular Analysis of the VH Gene Usage in a Familial Case of Waldenstrom's Macroglobulinemia.

Abstract

Waldenstrom's Macroglobulinemia (WM) is a rare lymphoproliferative disorder characterized by lymphoplasmacytic infiltration of the bone marrow and/or other tissues and the presence of a serum monoclonal IgM. The etiology of the disease is still unknown but the identification of family clusters may contribute to the understanding of its pathogenesis. In this study we present a family with 4 members affected by WM consisting of three generations; 2 sisters of the first generation were both suffering from WM. One of them presented to our section with mild anemia, a monoclonal serum IgM compound, 80% infiltration by lymphoplasmacytes in the bone marrow and the diagnosis of WM was made. Her sister was also suffering from WM but followed in another Centre. Our patient had two sons that at the age of 52 and 46 years presented a serum monoclonal IgM. At presentation, the first one had a monoclonal IgM value of 1680 mg/dl and a 40% BM lymphoplasmacytic infiltration with no other findings, signs or symptoms; he is regularly followed in our section for 30 months and his disease is stable. The second son, presented with a serum monoclonal IgM value of 886 mg/dl and a 10% BM infiltration by monoclonal lymphoplasmacytes and plasmacytes and was initially characterized as having an IgM-MGUS; while under follow-up examination only, he developed peripheral neuropathy with positive anti-Mag antibodies and improved with rituximab administration. Nor the mother or the sons had HCV antibodies. The first son has 3 children and the second two. Buccal and blood DNA was analysed for the IgH rearrangement by PCR. The PCR products after ligation and cloning were sequenced in an automated sequencer. Sequences obtained from each sample were aligned with germline sequences in the BLAST directory. No Ig rearrangements were detected in buccal DNA. Monoclonality was demonstrated in all affected members and in 2 healthy individuals of the third generation by PCR while immunophenotyping did not show evidence of disease in those two members. VH3 family was expressed at the highest frequency (80%). Different gene segments were recognized for the analysed sequences. D segments were attributed in all sequences. All affected and 1 healthy member had mutated VH genes. This is the first study of a family with WM consisting of three generations and reporting blood monoclonality of healthy individuals by molecular methods. The biologic value of the finding remains to be seen. Further study and a long follow-up is needed to clarify this issue.