What is pediatric mixed connective-tissue disorder (MCTD)?

Updated: Oct 24, 2018
  • Author: Marisa S Klein-Gitelman, MD, MPH; Chief Editor: Lawrence K Jung, MD  more...
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Answer

Sharp and colleagues first proposed mixed connective tissue disease (MCTD) as a separate autoimmune disorder. [1] The initial definition identified patients with a specific autoantibody profile, high titers of anti-U1 ribonucleoprotein (70-kD) autoantibody (anti-RNP Ab) but without anti-Smith autoantibody (anti-Sm Ab), in association with specific clinical criteria. Alarcon-Segovia and Villareal and Kasukawa et al subsequently suggested 2 alternate sets of criteria. [2, 3] A comparison of the sensitivity and specificity of the above 3 sets of criteria along with a fourth set of criteria developed by Kahn et al demonstrated that the Kahn and Alarcon-Segovia criteria are the most sensitive and specific for disease diagnosis. [4]

In pediatrics, Kasukawa criteria are used most frequently in published series and have more conservative requirements. Mixed connective tissue disease remains a controversial diagnosis. Some rheumatologists view mixed connective tissue disease as a separate disease; others classify the disorder as an undifferentiated connective tissue disease or overlap syndrome, which may have features of lupus, progressive systemic sclerosis, rheumatoid arthritis, and myositis but should not have its own separate name. [5, 6]

Adding support to the concept of mixed connective tissue disease as a distinct entity, in 1993, Mairesse et al described an autoantibody to the constitutive 73-kD heat shock protein found at high levels exclusively in patients with mixed connective tissue disease. [4] This autoantibody was found in reduced levels in patients with progressive systemic sclerosis and rheumatoid arthritis. The autoantibody was not found in significant quantities in patients with systemic lupus erythematosus (SLE) or myositis. This finding has not been duplicated and must be interpreted with caution. However, the authors redefine mixed connective tissue disease as "a core of minor symptoms (ie, Raynaud phenomenon, puffy fingers, mild myositis, and arthritis) associated significantly with anti-U1-68kD antibody, defining an undifferentiated connective tissue (UCTD) disease that may ultimately overlap with features of major connective tissue disease."

Although confusing, perhaps the best way to consider mixed connective tissue disease is as an undifferentiated connective tissue disease represented mostly by Raynaud phenomenon and anti-RNP antibody. See the image below.

Raynaud phenomenon showing demarcation of color di Raynaud phenomenon showing demarcation of color difference.

This disorder may evolve into one of several major connective tissue diseases or to an overlap syndrome of the major connective tissue diseases. The evolution of this disease requires the physician to carefully assess and constantly reassess the patient in anticipation of change and to provide early intervention with appropriate medical therapy.


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