Disorder of immunoglobulin synthesis in which large quantities of abnormal heavy chains are excreted in the urine; amino acid sequences of the n-(amino-) terminal regions of these chains are normal, but they have a deletion extending from part of the variable domain through the first domain of the constant region, so that they cannot form cross-links to the light chains; the defect arises through faulty coupling of the variable (v) and constant (c) region genes.

Heavy chain disease is a form of paraproteinemia and plasma cell dyscrasia that involves the proliferation of cells producing immunoglobulin heavy chains. This disease is characterized by an excessive production of heavy chains that are short and truncated. These heavy chain disease proteins have various deletions, mainly in their amino-terminal part, which causes the heavy chains to lose the ability to form disulfide bonds with the light chains...