MAUI, HAWAII – The 15% rule in scleroderma is a handy tool that raises awareness of the disease’s associated prevalence of various severe organ complications so clinicians can screen appropriately, Janet Pope, MD, said at the 2020 Rheumatology Winter Clinical Symposium.
Bruce Jancin/MDedge News
Dr. Janet Pope
Dr. Pope and colleagues in the Canadian Scleroderma Research Group developed the 15% rule because they recognized that scleroderma is rare enough that most physicians practicing outside of a few specialized centers don’t see many affected patients. The systemic autoimmune disease is marked by numerous possible expressions of vascular inflammation and malfunction, fibrosis, and autoimmunity in different organ systems.
“A lot of clinicians do not know how common this stuff is,” according to Dr. Pope, professor of medicine at the University of Western Ontario and head of the division of rheumatology at St. Joseph’s Health Center in London, Ont.
Basically, the 15% rule holds that, at any given time, a patient with scleroderma has roughly a 15% chance – or one in six – of having any of an extensive array of severe organ complications. That means a 15% chance of having prevalent clinically significant pulmonary hypertension as defined by a systolic pulmonary artery pressure of 45 mm Hg or more on Doppler echocardiography, a 15% likelihood of interstitial lung disease or clinically significant pulmonary fibrosis as suggested by a forced vital capacity less than 70% of predicted, a 15% prevalence of Sjögren’s syndrome, a 15% likelihood of having pulmonary artery hypertension upon right heart catheterization, a 15% chance of inflammatory arthritis, and a one-in-six chance of having a myopathy or myositis. Also, diastolic dysfunction, 15%. Ditto symptomatic arrhythmias.
“It’s a good little rule of thumb,” Dr. Pope commented.
The odds of having a current digital ulcer on any given day? Again, about 15%. In addition, scleroderma patients have a 15% lifetime risk of developing a complicated digital ulcer requiring hospitalization and/or amputation, she continued.
And while the prevalence of scleroderma renal crisis in the overall population with scleroderma is low, at 3%, in the subgroup with diffuse cutaneous systemic sclerosis, it climbs to 12%-15%.
Every rule has its exceptions. The 15% rule doesn’t apply to Raynaud’s phenomenon, which is present in nearly all patients with scleroderma, nor to gastroesophageal reflux disease or dysphagia, present in roughly 80% of patients.
Dr. Pope and coinvestigators developed the 15% rule pertaining to the prevalence of serious organ complications in scleroderma by conducting a systematic review of 69 published studies, each including a minimum of 50 scleroderma patients. The detailed results of the systematic review have been published.
Dr. Pope reported receiving research grants from and/or serving as a consultant to more than a dozen pharmaceutical companies.