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SUMMARY

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SUMMARY

The heavy-chain diseases (HCDs) are B-cell lymphoplasmacytic proliferative disorders in which neoplastic cells produce monoclonal immunoglobulins (Igs) consisting of truncated heavy chains (HCs) without attached light chains. The complex abnormalities of HCD proteins and the usual lack of normal light chains are a result of several distinct gene alterations, including somatic mutations, deletions, and insertions. HCDs involving the three main immunoglobulin classes have been described: α-HCD is the most common and has the most uniform presentation; γ- and μ-HCDs have variable clinical presentations and histopathologic features. The diagnosis is established from immunofixation of serum, urine, or secretory fluids in the case of α-HCD or by immunohistologic analysis of the proliferating lymphoplasmacytic cells in nonsecretory disease. Treatment of α-HCD consists of antibiotics. If there is no response to antibiotics or if aggressive lymphoma is diagnosed, chemotherapy is indicated. Treatment of γ- and μ-HCDs depends on the underlying clinicopathologic features rather than on the presence of the abnormal protein. Table 21–1 summarizes the features of the HCDs.

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TABLE 21–1.Summary of Features of the Heavy-Chain Diseases
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γ-HEAVY-CHAIN DISEASE DEFINITION AND HISTORY

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γ-Heavy-chain disease (HCD) is not a specific cytopathologic process; rather, it is a biochemical expression of a mutant B-cell clone. The disease should be considered a serologically determined entity with a variety of clinical and histopathologic features. It is defined by the recognition of monoclonal deleted gamma (γ) chains devoid of light chains.1

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The first case of γ-HCD was described in 1964 by Franklin and colleagues,2 who observed a homogeneous band between γ- and β-globulin in an African American patient with generalized lymphadenopathy. Comparison of the proteins in the urine to those in the serum showed that they were the same, a suggestion of the presence of a low-molecular-weight serum γ-globulin, which then was shown to be ...

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