Two Cases of Heavy Chain MGUS

Heavy chain diseases are rare variants of B-cell lymphomas that produce one of three classes of immunoglobulin heavy chains,without corresponding light chains. We describe two patients with asymptomatic heavy chain monoclonal gammopathy. The firstpatient is a 51-year-old woman with alpha paraprotein on serum immunofixation. The second case is a 46-year-old woman withgamma paraprotein on urine immunofixation. Neither patient had corresponding monoclonal light chains. Workup for multiplemyeloma and lymphoma was negative in both patients. These two cases illustrate that heavy chain monoclonal gammopathy canexist in the absence of clinically apparent malignancy. Only a few reports of “heavy chain MGUS” have been described before. Inthe absence of specialized guidelines, we suggest a similar follow-up as for MGUS, while taking into account the higher probabilityof progression to lymphoma than to myeloma