History
The presenting signs and symptoms of mu heavy chain disease (mu-HCD) are generally secondary to the associated hematologic disorder, such as chronic lymphocytic leukemia (CLL), lymphoproliferative disorder, or myeloma. Patients may show evidence of systemic disease, such as weight loss, fever, night sweats, and recurrent infection. [9]
The first reported cases of mu-HCD had a clinical picture consistent with CLL; however, with better diagnostic procedures and increased awareness of the disease, the defining heavy chain protein has been observed in a broader range of clinical settings. Currently, only one third of patients with mu-HCD appear to have CLL. In a review of 150 consecutive patients with CLL, thorough investigation of serum proteins failed to identify a single instance of mu-HCD, which suggests an incidence of less than 1% in this population. [10]
Various clinical presentations of mu-HCD have since been identified, including a presentaiton of monoclonal gammopathy without any identified symptoms of B-cell lymphoma (20%). [11] In 10% of cases, an intact IgM protein is simultaneously detected in the serum. Another 10% of cases were associated with clinical multiple myeloma or plasmacytoma. Mu-HCD is also reported to be associated with systemic amyloidosis in rare instances. [9]
Physical Examination
Physical examination findings are variable in patients with mu-HCD, but may include the following:
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Splenomegaly is almost universal.
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Hepatomegaly is noted in 25% of cases.
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Peripheral lymphadenopathy is present in 40% of cases.
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Bone pain from lytic lesions is present in 40% of cases.
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Pallor may be noted if significant anemia is present, which is usually observed only in advanced disease.
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Normal immunoglobulin molecules consist of 2 pairs of polypeptide chains, designated the light and heavy chains, which are interconnected by disulfide bonds. Courtesy of OpenStax (Rice University).
