Mixed connective tissue disease (MCTD), a chronic disorder that has overlapping features of two or more systemic rheumatic disorders, is a relatively stable disease that is milder than systemic lupus erythematosus and systemic sclerosis, new research from Norway shows. However, most patients failed to achieve long-term remission.
The study, “Disease evolution in mixed connective tissue disease: results from a long-term nationwide prospective cohort study,” published in the journal Arthritis Research and Therapy, may have an impact on how clinicians manage mixed connective tissue disease in patients.
MCTD is characterized by the presence of elevated amounts of anti-ribonucleoprotein (RNP) antibodies and overlapping symptoms of two or more rheumatic disorders: systemic sclerosis (SSc), systemic lupus erythematosus (SLE), polymyositis, and rheumatoid arthritis (RA).
Although MCTD was defined as a separate disease in 1972, controversy has existed about whether it is a separate and stable phenotype or a transient one.
Researchers at the University of Oslo, in Norway, set out to assess the phenotypic stability and remission of MCTD and to determine whether they are influenced by clinical parameters.
The study involved 118 MCTD patients — from what is known as the Norwegian nationwide MCTD cohort — recruited from all of Norway’s rheumatology departments from 2005-2008.
Clinical parameters, including pulmonary function, computed tomography, and routine blood tests, were assessed at two points in time: when the cohort was established, and when the current study was conducted (an average of seven years after the first point).
During the study period, only 14 patients (12%) developed a specific rheumatic condition (SLE, SSc, or RA). The remaining 104 patients had a stable MCTD phenotype, meaning they did not evolve to another condition.
In an effort to identify a predictor of MCTD phenotype stability, researchers found that only the presence of puffy hands at the first time point qualifies as a predictor.
Patients with a stable MCTD phenotype showed a decrease in disease activity, such as arthritis, rash, digital ulcers, and alopecia (hair loss) over time. Overall, 46 percent of patients with a stable MCTD phenotype were in remission at the second time point, while 13 percent were defined as having durable remission, meaning they were in remission throughout the study, including the first time point. Thirty percent were defined as having extended remission, meaning they had active disease at the first time point but achieved remission during the observation period.
A higher forced vital capacity at the first time point was found to be associated with achieving and remaining in remission. On the other hand, patients with thrombocytopenia (low blood platelet count) and those using nonsteroidal anti-inflammatory treatments at the first time point were less likely to be in remission.
Taken together, the findings indicate that “the majority of patients with MCTD retain their phenotype during long-term observation and MCTD involves milder disease activity than SSc and SLE,” the team reported.