Mixed connective tissue disease (MCTD) occurred with an annual incidence of 1.9 cases per 100,000 individuals in a population-based study of adults conducted during 1985-2014 in Olmsted County, Minnesota.
The study also is the first to report a standardized mortality ratio for MCTD, at 1.1 (95% confidence interval, 0.4-2.6), which was not different from the general population, according to Dr. Patompong Ungprasert and other researchers from the Mayo Clinic, Rochester, Minn. They identified Raynaud’s phenomenon as the most common initial symptom of MCTD (in 50% of patients), followed by arthralgia (30%) and swollen hands (16%).
The proportion of patients whose MCTD evolved to other diagnoses was relatively low, occurring in only 10% of the cohort (4% to systemic sclerosis and 6% to systemic lupus erythematosus), corresponding to 10-year rates of 6.3% and 8.5%, respectively. The findings serve as additional “evidence to support the existence of MCTD as distinct entity, not just a transitional stage to other connective tissue diseases,” wrote the investigators, who reviewed data from 50 patients who met criteria for MCTD.
Read the full study in Arthritis Care & Research.