Mixed Connective Tissue Disease - MCTD

Mixed connective tissue disease (MCTD) is a complex, systemic, autoimmune disease and generally is described as an overlap syndrome.  Clinically, patients exhibit varied combinations of features common to other systemic autoimmune rheumatic diseases (SARDs) such as systemic lupus erythematosus (SLE), polymyositis, dermatomyositis, systemic sclerosis (SSc) (scleroderma),  and rheumatoid arthritis.  MCTD can range from treatable illness to potentially life-threatening disease that may involve the lungs, kidneys, gastrointestinal system, or central nervous system.  Although MCTD can occur at any age, the average age of onset is 37-40 years,   and the disease is more prevalent in women than in men.  Early diagnosis is important because it may enable prevention of some of the more severe complications of MCTD, such as lung fibrosis.  However, diagnosis can be challenging because patients with MCTD may meet criteria for other connective tissue diseases or SARDs.   Diagnosis typically requires clinical examination, a thorough patient history, and laboratory testing for antinuclear antibodies (ANAs) as well as antibodies against U1 small nuclear ribonucleoprotein (anti-U1 RNP antibodies or anti-Smith/RNP antibodies). The presence of significantly elevated levels of anti-Smith/RNP (Sm/RNP) antibodies associated with the ANA speckled pattern, as detected by an indirect immunofluorescence antibody (IFA) assay, is a distinguishing characteristic of MCTD.   Laboratory testing in the initial workup for MCTD may also include autoantibody tests to help differentiate SARDs, serum immunoglobulin testing, and tests for other markers to evaluate systemic inflammation.

Tabs Content
Content Review: 
June 2019

Last Update: November 2019