There is a fairly wide range in survival rates associated with the different autoantibodies, from a five-year survival of 100% for anti-PM-Scl to 76% for anti-U3RNP. Dr. Medsger drew particular attention to large drop-offs in survival between five and 10 years for certain autoantibodies.
The five-year rate for anti-Ku is 83%, but the 10-year survival falls to 55%; the drop for anti-topo I is from 83% to 65%; and for anti-U3RNP, it is 76% at five years down to 60% at 10 years.
“A number of antibodies show a significant decrement in survival between five and 10 years,” he said. “I think we can explain many of them by internal organ involvements, particularly pulmonary fibrosis and pulmonary arterial hypertension.” A research paper has shown a large difference in survival in SSc-linked renal crisis between anti-topo I and anti-RNA polymerase III.2 Work in Dr. Medsger’s lab has borne this out, showing that the primary result of renal crisis among SSc patients with anti-topo I was death, while the main outcome for those with anti-RNA polymerase III was no dialysis requirement at all. He said it is likely that SSc-associated comorbidities associated with anti-topo I, such as interstitial lung disease and cardiac involvement, drive the poorer outcomes.
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“There are perhaps explanations for this finding, but they need to be looked into,” he said.
There is also a wide range in survival in SSc-linked pulmonary arterial hypertension, with a rate of 33% at 10 years for anti-Th/To and just 13% for anti-centromere.
“Perhaps this difference relates, in part, to the fact that anti-centromere antibody patients are older, and that they have nonscleroderma comorbidities,” Dr. Medsger said. “But I think from the point of view of planning clinical trials, one has to be aware that there are differences between SSc autoantibody subsets in the natural history of the disease and its complications.”
Thomas Collins is a freelance medical journalist based in Florida.
References
- Shanmugam VK, Swistowski DR, Saddic N, Wang H, Steen VD. Comparison of indirect immunofluorescence and multiplex antinuclear antibody screening in systemic sclerosis. Clin Rheumatol. 2011;30:1363-1368.
- Codullo V, Cavazzana I, Bonino C, et al. Serologic profile and mortality rates of scleroderma renal crisis in Italy. J Rheumatol. 2009;36:1464-1469.
