Fd Deficiency and Molecular Size of Scleromyxedema Monoclonal Immunoglobulins

Recently, Fd deficiency of the monoculonal IgG-lambda immunoglobulin has been observed in a patient with scleromyxedema. The molecular weight of this paraprotein was 110,000 daltons. This stimulated the authors to perform similar investigations in 2 cases. After purification of the monoclonal immunoglobulins (both IgG sub(1)-lambda) by isoelectric focusing, these were subjected to immunoelectrophoresis with anti-Fd and anti-Fab antisera and analytical ultracentrifugation. No Fd deficiency could be detected by immunoelectrophoresis, the molecular weight of monomeric immunoglobulins calculated from ultracentrifugation was approximately 160,000 daltons. These results are in accordance with amino acid analysis of the monoclonal immunoglobulin of an early described case with papular mucinosis, which did not show substantial differences from normal IgG.