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DEFINITION

  • The heavy-chain diseases (HCDs) are neoplastic disorders of B cells that produce monoclonal immunoglobulins (Ig) consisting of truncated heavy chains without attached light chains.

  • In decreasing order of incidence, HCD involves synthesis of defective α, γ, or μ heavy chains.

  • The diagnosis is established from immunofixation of serum, urine, or secretory fluids in the case of α-HCD or from immunohistologic analysis of the proliferating lymphoplasmacytic cells in nonsecretory disease.

  • There is a high frequency of autoimmune disorders preceding or concurrent with the diagnosis of HCD, particularly γ-HCD.

  • Table 71–1 summarizes the clinical features of the three types of HCD.

TABLE 71–1SUMMARY OF FEATURES OF THE HEAVY-CHAIN DISEASES

ETIOLOGY AND PATHOGENESIS

  • In α-HCD, the lymphoplasmacytic infiltration of the intestinal mucosa is thought to be a response of the alimentary tract immune system to protracted luminal antigenic stimulation. A causal relationship between infection and pathogenesis is supported by a response to antibiotics in some cases.

  • The etiology of γ-HCD and μ-HCD is unknown.

CLINICAL AND LABORATORY FEATURES

α-HCD

  • This form of HCD is defined by the recognition of truncated monoclonal α chains without associated light chains.

  • The characteristic sharp spike of monoclonal gammopathy is not found on serum protein electrophoresis.

  • Identification of the α-HCD protein depends on immunoselection or immunofixation.

  • Majority of cases have been reported in northern Africa, Israel, and surrounding Middle Eastern countries.

  • At presentation, the patients commonly are in their teens or early twenties.

  • Common clinical features on presentation include recurrent or chronic diarrhea, weight loss, fevers, and/or growth retardation.

  • Digital clubbing is a frequent finding.

  • Moderate hepatomegaly occurs in about 25% of patients.

  • Mesenteric lymphadenopathy is common, sometimes presenting as an abdominal mass, whereas extra-abdominal lymphadenopathy is rare.

  • In many cases, the abnormal heavy chain only can be found in the intestinal secretions.

  • The jejunum is the usual ...

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