Based on a cohort in Minnesota from 1985 through 2014, researchers found the yearly occurrence of mixed connective tissue disease to be two people per 100,000.
Using individual medical record review, Patompong Ungprasert, MD, in the Division of Rheumatology at the Mayo Clinic in Minnesota, and colleagues assessed a cohort based in Olmsted County, Minnesota. Diagnosis of mixed connective tissue disease (MCTD) required fulfillment of at least one of the four widely accepted criteria. The researchers also collected data on demographic characteristics, clinical presentation, laboratory investigations and mortality.
The researchers found 50 cases of MCTD. Of the cases, the mean patient age was 48.1 years and 84% were female. The annual incidence was 1.9 per 100,000. Before diagnosis, 50% had Raynaud’s phenomenon; 30% had arthralgia; and 16% had swollen hands. After diagnosis — which took a median time of 3.6 years from first symptom onset — 86% had arthralgia, 80% had Raynaud’s phenomenon, 64% had swollen hands, 44% had leukopenia or lymphopenia and 38% had heartburn. The 10-year evolution rate from MCTD was 8.5% to lupus and 6.3% to systemic sclerosis. The overall mortality ratio in those with MCTD to the general population was 1.1, with no significant difference.
The researchers wrote this was the first population-based study of MCTD to fully describe the epidemiology and clinical characteristics of the disease. – by Will Offit
Disclosure: The researchers report a grant from the NIH.