Abstract
BackgroundThe phenotypic stability of mixed connective tissue disease (MCTD) is not clear, and knowledge about disease activity and remission is scarce. We aimed to establish the occurrence of evolution from MCTD to another defined rheumatic condition, and the prevalence and durability of remission after long-term observation.MethodsIn this large population-based prospective observational MCTD cohort study (N = 118), disease conversion was defined by the development of new auto-antibodies and clinical features compliant with another well-defined rheumatic condition. Remission was defined by a combination of systemic lupus erythematosus disease activity index 2000 (SLEDAI-2 K) of 0 and European League Against Rheumatism scleroderma trials and research (EUSTAR) activity index <2.5. Predictors of phenotypic stability and disease remission were assessed by logistic regression.ResultsAmong 118 patients, 14 (12%) developed another well-defined rheumatic condition other than MCTD after mean disease duration of 17 (SD 9) years. Puffy hands predicted a stable MCTD phenotype in univariable regression analysis (OR 7, CI 2–27, P = .010). Disease activity defined by SLEDAI-2 K, decreased gradually across the observation period and > 90% of patients had EUSTAR activity index <2.5. There were 13% patients in remission throughout the whole mean observation period of 7 (SD 2) years. The strongest predictor of remission was percentage of predicted higher forced vital capacity.ConclusionsOur results strengthen the view of MCTD as a relatively stable disease entity. Long-term remission in MCTD is not frequent; however, the low SLEDAI-2 K and EUSTAR scores during the observation period suggests that the disease runs a milder course than systemic lupus erythematosus and systemic sclerosis.
Highlights
The phenotypic stability of mixed connective tissue disease (MCTD) is not clear, and knowledge about disease activity and remission is scarce
Characteristics of the Norwegian MCTD cohort Altogether, 16 of the 147 patients from the original nationwide cohort had died before the reexamination at time point time point 2 (T2), while 13 were lost to follow up (Fig. 1)
The prevalence and prediction of phenotype stability Clinical examinations and auto-antibody profiles analyzed in the 118 longitudinally observed patients demonstrated that 14 patients (9%) had evolved to another specific rheumatic condition during the observation period (Fig. 1; Additional file 1)
Summary
The phenotypic stability of mixed connective tissue disease (MCTD) is not clear, and knowledge about disease activity and remission is scarce. The studies by Van den Hoogen [9], Gendi [5] and Ungprasert [7] regarded patients as having evolved from MCTD when they met one or more of the classification criteria for SLE, SSc and RA, reporting on patients evolving from MCTD to overlap syndromes. This can be viewed as contradictive when MCTD is defined as a specific overlap syndrome. There is a distinct lack of data on the durability and stability of remission in this disorder
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