The dramatic increase in complement levels was due the development of a monoclonal gammopathy which was discovered by serum protein electorphoresis. The IgM antibodies bound to c3 and c4 created a soluble immune complex which generated spurious light scattering signals, resulting in falsely elevated nephelometric immunoassay results for C3 and C4. Immunoprecipitation of plasma IgM prior to repeating the complement measurements reduced the C3 and C4 levels to 0.6 and 0.16 g/l, respectively.
Features uncommon to Waldenstrom's Macroglobulinemia seen in this case include the age of onset, the acute development of the monoclonal gammopathy and the laboratory abnormalities which led to the presumptive diagnosis. Generally waldenstrom's macroglobulinemia is a disease of the elderly, presenting between the sixth and seventh decade of life. Clinical presentation is characterized by features related to a hyperviscosity syndrome. The opportunity to see the rapid development of a monoclonal gammopathy where levels of immunoglobulin increase more than 1 gram over the course of a year is coincidental since this patient had been serologically monitored due to the nature of her Systemic Lupus Erythematosus.
The prevalence of monoclonal gammopathy in patients with Systemic Lupus Erythematosus is rare, with less than four documented cases since 1966.1,2,3,4 The relative risk for the development of a monoclonal gammopathy in SLE patients is greater than the general population,1 however, the clinical and pathologic significance of this association has yet to be elucidated.
A possible association between Systemic Lupus Erythematosus and cancer has been suggested, but not definitely proved in sefveral case reports8,9, small series10,11,12, or cohort studies13-16. A cohort study by S. Manzi et.al., at the University of Pittsburgh Medical Center demonstrated an increased trend in lymphoproliferative disorders in patients with Systemic Lupus Erythematosus17.
Contributed by Valerie Lyons, M.D. and Robert Kelly, Ph.D.