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Mixed connective tissue disease (MCTD)

Mixed connective tissue disease (MCTD), or: Sharp syndrome, is an uncommon, specifically defined, overlap syndrome. MCTD should be suspected when additional overlapping features are present in patients appearing to have rheumatoid arthritis, SLE, scleroderma, or polymyositis. MCTD is characterised by very high titres of circulating antinuclear antibodies (ANA) to a ribonucleoprotein antigen (RNP).

Hand swelling, Raynaud’s syndrome, polyarthralgia, inflammatory myopathy, esophageal hypomotility, and pulmonary dysfunction are common. Diagnosis is by the combination of clinical features, ribonucleoprotein antibodies, and absence of antibodies specific for other autoimmune diseases.

Tests for antinuclear antibodies (ANA), RNP antibodies, and antibodies to ENA are done first. If results of these tests are compatible with MCTD (RNP antibodies very high, positive ANA!), tests for rheumatoid factors, Jo-1 antibodies, antibodies to the ribonuclease-resistant Smith component of ENA (Sm antibodies), and double-stranded DNA (dsDNA antibodies) are done to exclude other possible diagnoses.

Further evaluation depends on symptoms and signs; manifestations of myositis, renal involvement, or pulmonary involvement prompt tests of those organs (eg., creatine kinase, magnetic resonance imaging, electromyogram, or muscle biopsy for diagnosis of myositis).

Almost all patients have high titres of fluorescent ANA producing a speckled IFA pattern. Antibodies to ENA are usually present at very high titres. RNP antibodies are detectable, whereas Sm antibodies are absent. Rheumatoid factors are frequently positive, and titres are often high. The erythrocyte sedimentation rate (ESR) is frequently elevated.

Treatment of mixed connective tissue disease varies with disease severity and organ involvement but usually includes corticosteroids and sometimes additional immunosuppressants.



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  1. I recently tested pos for mildly elevated anti rnp and normal Ana. I have been on strong anti inflammatory since August. . Many soft tissue problems..tendonitis in 8 joints, 2 ted swollen fumgers with clean xrays,5 trigger fingers, back and neck
    Back and neck are chronic.
    Any ideas where to go from there? Family doc first said labs were wnl then when I asked about the rnp he suggested I see a rheumatoid doc. But can’t get in until August.

    1. Dear Tammy,

      first of all, I want to emphasize, that you should NOT quest for personal medical advice via the internet. Every disease is individual, and under different circumstances, similar symptoms may have different causes. Especially inflammatory rheumatic diseases are challenging to diagnose and to treat.
      I agree that you should see a specialized rheumatology doc to discuss your health concerns. He or she will give you advice, e.g. about further diagnostic tests, while taking into account all clinical symptoms.

      Best whishes

  2. I’m wondering what is considered a high titre of RNP?
    I was under the impression that MCTD was diagnosed if the only positive ENA is the RPN and the absence of all others- Is that including ANA?
    I’m a bit confused.

    1. Friederike Hammar

      Diagnosis of autoimmune diseases is always a complex task, wich has to take into account the whole clinical picture, including clinical symptoms and laboratory findings.
      RNP antibodies are highly specific and sensitive markers for MCTD, but thy may also appear in some patients with other diseases like systemic lupus erythematosus or systemic sclerosis.
      ANA are directed against different structures of the cell nucleus and have to be specified according to the corresponding single antigens in the diagnostic workup, e.g by determination of anti-RNP if MCTD is suspected.
      Thus, most patients with MCTD will also have positive ANA/ENA results, and the detection of low titres of RNP antibodies in the absence of ANA should be interpreted with care. Normally, this does not indicate MCTD.
      Low/high antibody titres are not defined according to general values. Each laboratory has to evaluate and define their own reference values.

      1. i was diagnosed a year and a half ago with mctd and perscribed i have alittle scar tissue on lungs and i am on cellcept.. I thougt that i would be living a long healthy life and now this all pops up.. i fell like i am going downhill fast but everyone tells me i could live with this for 10 or more years. i am not reading that. i am upset.

        1. Friederike Hammar

          Hi Donna,

          I understand that you are struggeling with severe health problems and that you have to learn to live with your disease. Your physician should always be the first person to contact when you have questions related to your health.

          In addition there are orgaanisations that work for patients with autoimmune diseases and support them in their daily lives. In Europe for example, this is the EULAR pare organization
          In the US there is the American Autoimmune & Related Diseases Association, Inc.

          These organizations provide valuable resources for people living with autoimmune diseases.

          Wishing you all the best !

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