Patients with idiopathic inflammatory myositis are at high risk for hypertension and diabetes, but as a consequence of their disease rather than its treatment, a retrospective Australian study found.
Among patients with dermatomyositis, polymyositis, or inclusion body myositis, 62% and 29% had high blood pressure and diabetes mellitus, respectively, according to Vidya S. Limaye, MD, of the University of Adelaide, and colleagues.
In contrast, the background prevalence of hypertension and diabetes was considerably lower in the Australian adult population, at 9.4% and 4% respectively, the researchers wrote in the May International Journal of Rheumatic Diseases.
Inflammatory myositis is among a group of autoimmune diseases characterized by skeletal muscle weakness, elevated serum creatine kinase, and abnormalities seen on electromyography. These disorders often require long-term immunosuppression, usually with corticosteroids and second-line agents such as methotrexate.
However, prolonged use of corticosteroids has been linked to numerous adverse cardiovascular outcomes as well as to osteoporosis, cataracts, and increased risk of infections.
Epidemiologic studies have identified a strong association between atherosclerosis and other systemic autoimmune disorders such as rheumatoid arthritis and systemic lupus erythematosus, but the cardiovascular risk profile of patients with inflammatory myositis has not been previously studied.
The researchers initially set out to document the complications of corticosteroid and immunosuppressive treatment among patients with myositis. So Limaye and colleagues conducted a review of medical records and pathology reports from 344 patients who were enrolled in the South Australian myositis database between 1980 and 2009.
However, they found themselves “surprised by an extremely high background prevalence of hypertension and diabetes mellitus in our cohort,” the authors wrote.
The database included 43 patients with a histologic diagnosis of dermatomyositis, 184 with polymyositis, and 117 with inclusion body myositis.
Patients with dermatomyositis were younger, with a mean age at diagnosis of 53 years, while those with polymyositis and inclusion body myositis had median ages of 59.1 years and 67.8 years, respectively.
All patients with dermatomyositis had been treated with prednisone, as had 90% of patients with polymyositis, and 71% of those with inclusion body myositis.
The most commonly used immunosuppressive drugs were methotrexate, used in 83 patients, and azathioprine, given to 48 patients. Smaller numbers received hydroxychloroquine, cyclosporine, mycophenolate mofetil, and intravenous immunoglobulin.
The researchers first considered the presence or absence of comorbidities regardless of the timing of treatment in relation to a diagnosis of myositis.
In addition to the high prevalence of hypertension and diabetes, osteoporosis was also more prevalent in those with myositis compared with the overall Australian adult population (32% versus 3.4%).
Ischemic heart disease and cataracts each were present in 26%, while cardiovascular disease and hyperlipidemia each were found in 13%.
To clarify whether these comorbidities were related to the long-term immunosuppressive treatment, the researchers analyzed data from patients for whom information was available on whether the complication occurred before or after their myositis diagnosis.
“In the absence of a treatment effect on the proportion of patients with the comorbidity, the pre- and postdiagnosis proportions should approximate 50%,” they explained.
Compared with the high (62%) prevalence of hypertension found at any time, in only 24% was high blood pressure detected after the myositis diagnosis (P
Osteoporosis occurred more frequently after diagnosis, but this was not statistically significant (P=0.09). There were no increases in proportions of patients with other comorbidities in the postdiagnosis period.
The investigators also analyzed the presence of comorbidities according to the individual myositis subtypes and found that patients with dermatomyositis were more likely to have hypertension, diabetes, and cataracts as a result of treatment rather than as preexisting conditions.
This, they said, reflects the significantly younger age of the dermatomyositis patients.
In contrast, patients with all subtypes were at equal risk of infectious complications including herpes simplex virus infections and pneumonia.
In discussing their findings of high prevalence of diabetes and hypertension in these autoimmune patients, Limaye and colleagues noted that specific autoimmune mechanisms are believed to contribute to the development of hypertension.
Autoantibodies against ??1-adrenergic receptors and angiotensin II, while playing a role in hypertension, also may crossreact with myositis autoantigens and stimulate an inflammatory response in skeletal muscle, they said.
Furthermore, the excess prevalence of diabetes and hypertension in these patients may represent a link with the metabolic syndrome.
“Indeed, skeletal muscle insulin resistance is fundamental in the pathogenesis of the metabolic syndrome and recent evidence suggests inflammatory cytokines (adipokines) and aberrant activity of the renin-angiotensin-aldosterone system (also linked with hypertension) may provide a link between inflammation and insulin resistance in skeletal muscle,” they wrote.
This study had limitations, including possible selection bias, confounding factors such as age and sex, and its retrospective design.
Nonetheless, the “very high prevalence” of hypertension, diabetes, and ischemic heart disease indicates that a comprehensive assessment of cardiovascular risk is essential in patients with inflammatory myositis, they concluded.
Nancy Walsh, Contributing Writer, MedPage Today
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner