Urinary mercury levels in patients with autoantibodies to U3-RNP (fibrillarin)

Objective. Autoantibodies to the U3 nucleolar ribonucleoprotein (RNP) fibri llarin occur in some patients with systemic sclerosis (SSc) or other connec tive tissue diseases and can be induced in certain mouse strains by injecti ons of mercuric chloride, perhaps due to antigenic alteration of fibrillari n by mercury (Hg). Thus, potential occult exposure to Hg was explored in pa tients with SSc. Methods. Urinary Hg levels were measured by cold vapor atomic absorption in 13 patients with antifibrillarin antibodies (11 with SSc), 39 SSc patients without antifibrillarin antibodies. and 32 healthy controls. Results. Mean urinary Hg levels were significantly elevated in the antifibr illarin antibody positive patients compared to those in other patients with SSc and controls. After correction for urinary creatinine levels, mean uri nary Hg levels remained significantly different than in the other 2 groups, although Hg levels in all were still within the normal or "unexposed" rang e. When patients and controls with low urinary creatinine levels were exclu ded from analysis, there were no significant differences in mean urinary Hg levels among the 3 groups. Conclusion. These findings suggest that further epidemiological and basic r esearch studies of mercury are warranted in patients with SSc, especially t hose expressing antifibrillarin antibodies.