Hypocomplementemia in Systemic Sclerosis — Clinical and Serological Correlations

MARIE HUDSON, JENNIFER G. WALKER, MARVIN FRITZLER, SUZANNE TAILLEFER, Canadian Scleroderma Research Group, MURRAY BARON

ABSTRACT.

Objective. Although complement fixation is not commonly thought to be part of the pathogenesis of systemic sclerosis (SSc), hypocomplementemia has been associated with SSc. We hypothesized that hypocomplementemia in SSc might indicate the presence of overlap disease. We investigated if SSc patients with hypocomplementemia had more features of overlap disease than those with normal complement levels.

Methods. Study subjects consisted of those enrolled in the Canadian Scleroderma Research Group Registry. Patients were divided into 2 groups: those with normal complement levels (normal C3 and C4) and those with hypocomplementemia (low C3 or C4). Evidence of overlap disease was defined as physician reports of other specific rheumatic conditions. Autoantibodies were assayed. Differences in rates of concomitant diseases and in antibody profiles were compared between groups.

Results. Our study included 321 patients (88% women, mean age 56 ± 13 yrs, mean disease duration 11 ± 9 yrs). Of these, 276 (86%) had normal complements and 45 (14%) had hypocomplementemia. Patients with hypocomplementemia were significantly more likely to have physician-reported inflammatory myositis (27% vs 12%; p < 0.008) and vasculitis (11% vs 2%; p < 0.011) than those with normal complement. There was also a trend toward more antichromatin antibodies (18% vs 9%; p = 0.051) in patients with hypocomplementemia compared to normals.

Conclusion. Hypocomplementemia may identify a particular subgroup of SSc patients who have overlap disease. (First Release Oct 15 2007; J Rheumatol 2007;34:2218-23)

Key Indexing Terms:

SCLERODERMA
COMPLEMENTS
AUTOIMMUNE DISEASE
CLASSIFICATION

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From SMBD–Jewish General Hospital and McGill University, Montreal, Quebec; and University of Calgary, Calgary, Alberta, Canada.

Supported by the Canadian Institutes of Health Research, the Scleroderma Society of Canada, and educational grants from Actelion Pharmaceuticals and Pfizer. Dr. Hudson is a New Investigator funded by the Canadian Institutes of Health Research.

M. Hudson, MD, MPH; S. Taillefer, PhD; M. Baron, MD, SMBD–Jewish General Hospital and McGill University; J.G. Walker, MD; M. Fritzler, MD, University of Calgary.

Address reprint requests to Dr. M. Hudson, SMBD-Jewish General Hospital, Room A-216, 3755 Cote Ste. Catherine Road, Montreal, Quebec H3T 1E2. E-mail marie.hudson@mcgill.ca

Accepted for publication July 22, 2007.

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