δ-Heavy chain disease: A study of a case

Abstract

In this report we describe a new case of heavy chain disease, in which the serum M-component protein reacted with anti-IgD (δ monospecific) but not with other antisera of heavy or light chain specificity. Due to kidney lesion, the clinical course of this heavy chain disease was rapidly fatal. The main histopathological finding in the renal biopsy was a thickening of the glomerular basement membrane, presumably caused by depositions of the paraprotein. There were no pathological proteins in the urine. The clinical picture resembled that often seen in multiple myeloma, that is plasmocytoid morphology of the malignant cells and osteolytic lesions. The real heavy chain nature of the serum M component was ascertained in the present work by immunoelectrophoresis, by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) combined with an immunological detection of δ-heavy chain units, and by immunoselection. The molecular weight of the δ complex appeared to be about 260,000 daltons. Owing to the molecular weight of about 65,000 daltons obtained for the major subunit of the paraprotein molecule in SDS-PAGE, a tetrameric structure of the intact serum δ-chain paraprotein is suggested.