Gamma heavy chain "disease": heterogeneity of the clinicopathologic features. Report of 16 cases and review of the literature.

This review underscores the diversity of the clinical manifestations and hematopathological features of gamma heavy chain disease based on the detailed report of 16 patients evaluated in our chemical department, the analysis of 12 cases diagnosed in our laboratory, and the study of 81 cases previously reported. This condition is defined by the presence in the serum of immunoglobulin molecules composed of deleted gamma heavy chains devoid of light chains. The production by the monoclonal B cells of these peculiar proteins appears to result from multiple defects (deletions, insertions, and mutations) in both heavy and light chain genes leading to abnormal mRNA splicing. Gamma heavy chain disease is currently underdiagnosed. The diagnosis established by immunoelectrophoresis using specific antisera combined, in some instances, with the immunoselection procedure, can easily be missed on serum electrophoretic patterns: a narrow abnormal band suggestive of a monoclonal component was found in only 10 of our 28 cases. The amount of heavy chain disease protein in urine ranges from trace to 20 g/day and is usually moderate. Gamma heavy chain disease most often presents as a lymphoproliferative disorder featured by lymphadenopathies, splenomegaly, and constitutional symptoms. Extra-hematopoietic tumor localizations, such as cutaneous or subcutaneous involvement or thyroid tumor, may occur. Autoimmune disorders, notably rheumatoid arthritis and autoimmune hemolytic anemia or thrombocytopenic purpura, are frequent (26% of cases). There is no specific histological pattern. The most frequent is a pleomorphic malignant lymphoplasmacytic proliferation mainly seen in bone marrow and lymph nodes. Some cases present with a predominantly plasmacytic proliferation or chronic lymphocytic leukemia. Other patients are affected with non-Hodgkin lymphoma of various morphologic types. Immunocytologic studies showed that a gamma heavy chain disease protein may occur in the context of a double monoclonal lymphoproliferative process or in various B or T cell malignancies that are not directly involved in the production of the abnormal immunoglobulin. In some patients, the histologic appearance of the enlarged lymphoid organs showed only a moderate lymphoplasmacytic infiltration of uncertain malignancy. More important, some patients showed no evidence of an underlying lymphoproliferative disorder after several years of follow-up. The clinical course of gamma heavy chain disease varies from an asymptomatic state to a rapidly progressive malignancy. The choice of therapy should entirely rely on the underlying clinicopathologic features, without taking into account the presence of the abnormal protein.(ABSTRACT TRUNCATED AT 400 WORDS)