Raised blood clot risk for patients with inflammatory myopathies

By Megan Brooks

NEW YORK (Reuters Health) - Adults with polymyositis (PM) and dermatomyositis (DM) are at increased risk for venous thromboembolism (VTE), including deep venous thrombosis and pulmonary embolism, new research indicates.

"The risk is substantially higher during the first year after the diagnosis, (suggesting) that inflammation plays a key role in the pathogenesis of VTE in patients with PM and DM," Dr. Antonio Aviña-Zubieta, of the Arthritis Research Centre of Canada and University of British Columbia, told Reuters Health by email.

Inflammatory myopathies, including PM and DM, are rare connective tissue disorders characterized by chronic muscle inflammation and weakness and exact a high economic toll.

Despite several plausible mechanisms, the risk of VTE in this patient population is not well studied.

Using a British Columbia health database, the researchers identified 443 new cases of PM (58% women, mean age 60) and 355 new cases of DM (65% women, mean age 56). Forty six individuals had both PM and DM. Each case was matched with up to 10 controls.

"Overall, both PM and DM were significantly associated with an increased incidence of VTE as well as DVT (deep venous thrombosis) and PE (pulmonary embolism)," the researchers report in a paper online September 5 in Annals of Rheumatic Diseases.

Patients with PM had roughly an 8-, 6-, and 9-fold higher risk of VTE, DVT and PE, respectively, relative to population controls. "Similar trends were seen in DM," the authors say.

The risk of VTE and PE was highest during the first year after diagnosis of PM (25 and 38 times, respectively) and progressively attenuated over time. "Similarly, cases with DM had the highest risk during the first two years after diagnosis," the researchers report.

"The biological impact of inflammatory myopathies on risk of VTE may be higher in the initial years after diagnosis due to uncontrolled inflammatory activity before the full benefit of corticosteroid and/or disease-modifying antirheumatic drug therapy is achieved," they note in their article.

They say this is the first large population-based study to assess the risk of VTE in the PM/DM population.

"Given that VTE is the third most frequent cardiovascular complication in the general population and that some may be fatal (PE) it is important to be aware of these risks; especially considering that they can be prevented," Dr. Aviña-Zubieta told Reuters Health.

"Physicians should consider early and aggressive treatment of the underlying disease not only to control it, but also to prevent these complications. The role of anticoagulation in patients at high risk may be warrantied, but further research on this topic is needed," he said.

Funding for the study was provided by the Canadian Arthritis Network, The Arthritis Society of Canada, The British Columbia Lupus Society, the Canadian Institutes for Health Research (CIHR) and the Michael Smith Foundation for Health Research. The authors have declared no competing interests.

SOURCE: http://bit.ly/1sZUGIh

Ann Rheum Dis 2014.

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