Patients with both scleroderma and systemic lupus erythematosus (SLE) are younger at diagnosis, are more often women, and have less skin manifestations, but most importantly, show similar survival rates as those without lupus, according to a study.
The study, “Epidemiology and Survival of Systemic Sclerosis-Systemic Lupus Erythematosus Overlap Syndrome,” was published in The Journal of Rheumatology.
Approximately 20 percent of patients with scleroderma also have lupus. Symptoms of scleroderma may overlap with those of lupus, in both diffuse and limited cutaneous subtypes, which complicates diagnosis.
Prior studies reported that scleroderma patients with lupus are younger at scleroderma onset than those without lupus. Additionally, patients with the overlapping conditions usually have a higher incidence of Raynaud’s phenomenon — a condition caused by poor blood circulation that leads to painfully cold fingers and toes.
Despite these data, information on the incidence, clinical characteristics, and survival of patients with both conditions is still scarce.
To address this gap, researchers in Canada analyzed data from 1970 to 2017 from the Toronto Scleroderma Program, a health network comprising three academic hospitals in Toronto.
“To our knowledge, this is the largest study to evaluate the epidemiology of [scleroderma]-SLE in the modern era,” the researchers wrote.
The team identified 1,252 individuals, 16 or older, with scleroderma, 86 of whom also had lupus (6.8%). This incidence is slightly lower than what has been reported in other studies — ranging from 8.4% to 14.7% — the researchers noted.
Most scleroderma patients with lupus were women, 92% vs. 81% in those with just scleroderma, and the diffuse scleroderma subtype was seen less frequently in these patients than in those with scleroderma alone (12% vs. 35%).
Matching earlier reported data, patients with scleroderma and lupus were significantly younger at diagnosis than those without lupus — 37.9 versus 47.9 years. They were also more commonly East Asian (20% vs. 5.5%) or South Asian (12% vs. 5.1%).
Patients with both conditions more frequently had lupus anticoagulant (6% vs 0.3%) — referring to antibodies against factors that prevent blood clotting and are known to increase the risk of pulmonary arterial hypertension (PAH) and myocardial infarction — as well as anticardiolipin antibody (6% vs 0.9%) — common in people with lupus and other autoimmune diseases.
PAH was found more often among patients with scleroderma and lupus (52%) than those without lupus (31%).
Scleroderma patients with lupus also had less frequent calcium deposition in the skin or other body tissues, known as calcinosis (13% vs 27%), and telangiectasia (49% vs 75%), characterized by visible small blood vessels, or broken capillaries.
The data further revealed no differences in the frequency of digital ulcers (38% in scleroderma patients with lupus vs. 32% in scleroderma patients), renal crisis — including acute renal failure — (7% vs. 7%), interstitial lung disease (41% vs. 34%), hypertension (19% vs. 21%), diabetes (6% versus 6%), cancer (7% vs. 11%), and dyslipidemia (5% vs. 7%), which refers to an abnormal amount of lipids (fat) in the blood.
Importantly, the analysis suggested a similar median survival time in patients with the overlapping conditions (26.1 years) and those without lupus (22.4 years); the difference between the two groups was not statistically significant.
“It appears that having an overlap with SLE does not confer either an increased risk or protective effect for mortality,” the researchers wrote.
Most scleroderma patients with lupus who died during the study period had an unknown cause of death. Among the known causes were heart failure in two patients, sepsis — a complication from an infection — also in two patients, bowel obstruction in one patient, pulmonary embolism — the blockage of an artery in the lungs — in one patient, and myocardial infarction in one patient.
Overall, the team concluded: “SSc[scleroderma]-SLE overlap is not uncommon among those with SSc. SSc-SLE subjects are more frequently female, have a younger age at diagnosis, and less frequently have cutaneous manifestations of SSc.”
Nonetheless, “these subjects should be monitored for serious complications of SSc, including pulmonary hypertension, ILD [interstitial lung disease], renal crisis, and digital ulcers,” the researchers suggested.