A new case of gamma heavy chain disease: clinical, immunochemical and structural characterization

A new case of gamma heavy chain disease (gamma HCD) is described in a 77-year-old woman. The serum and urine contain an M-component and electrophoretic, antigenic and ultracentrifugal properties resembling those of the Fc fragment of IgG globulin. Analysis on SDS-polyacrylamide gel electrophoresis and ultracentrifugal studies show that gamma HCD portein is present in the serum as a dimer with a molecular weight of 58,000 daltons. Analysis of isotypic and allotypic markers along with the structural studies show that this HCD protein belongs to the IgG subclass and that deletion includes the total VH and CH1 regions with sequence starting at residue 225 in the middle of the hinge region.