Mixed Connective Tissue Disease (MCTD)

Mixed connective tissue disease (MTCD) is an autoimmune disease. With autoimmune diseases, your immune system malfunctions and attacks your own body. Rheumatoid arthritis (RA) is also an autoimmune disease.1

What is MCTD?

MCTD is sometimes called a rheumatic overlap syndrome. This is because people with MTCD have signs and symptoms of multiple connective tissue diseases. The most common connective tissue diseases include:1

MCTD typically causes symptoms of lupus, scleroderma, and myositis. However, people can have symptoms from other connective tissue diseases as well.1

There are other rheumatic overlap syndromes that may have similar symptoms to MCTD, like undifferentiated connective tissue disease (UCTD). However, MCTD is identified by a specific antibody in the blood. This antibody is called anti-U1-ribonucleoprotein (anti-U1-RNP).2

How is MCTD related to RA?

MCTD is not considered a common complication or comorbidity of RA, but the conditions have similarities. Doctors use the term comorbidity to describe a condition that occurs at the same time as another condition. Comorbid illnesses can interact in ways that make both conditions worse.2

MCTD and RA are both autoimmune diseases and can have similar signs and symptoms. MCTD can manifest in many ways. Some people may have symptoms that resemble RA.2

Like many autoimmune diseases, MCTD is not well understood. Some scientists believe MCTD is not its own disease and is just a subset of other connective tissue diseases, like RA. Other research has shown that MCTD could be an early sign of different connective tissue diseases, but this has not been confirmed.2

Symptoms

The symptoms of MCTD can vary. A person’s symptoms can also change over time. At different times, symptoms can more closely resemble different diseases. Some symptoms of MCTD include:1,3

  • Muscle and joint pain
  • Muscle weakness
  • Puffy, swollen fingers
  • White, numb fingertips, often in response to cold (this is sometimes called Raynaud's phenomenon)
  • Feeling very tired or having a light fever
  • Red or brownish rash on joints

Over time, MCTD may cause more serious complications. It sometimes affects the digestive tract and can cause heartburn or problems chewing and digesting food. MCTD can impact organs and increase the risk of other diseases. MCTD can cause kidney damage, heart disease, or lung disease. MCTD also may cause iron deficiency.4

Diagnosis

MCTD can be tricky to diagnose because the symptoms are similar to other diseases. Also, the symptoms can change and vary with time. Usually, a doctor will do a physical exam and a blood test. The physical exam will look for swollen hands and joints. The blood test will look for the presence of anti-U1-RNP. A positive test for anti-U1-RNP is a defining feature of MCTD.2

Treatment

Treatment for MCTD is focused on managing symptoms and complications. Treatment may depend on how serious the disease is, and which organs are impacted. Steroids can reduce inflammation and keep your immune system from attacking healthy cells. Immunosuppressant drugs will also limit the damage from your immune system.4

Your doctor may recommend medicines based on which other diseases your symptoms resemble. For example, antimalarial drugs are commonly used to treat lupus and can help if you have lupus-like symptoms. If your symptoms are more like RA, you may respond well to disease-modifying anti-rheumatic drugs (DMARDs), which are used for treating RA.1

Some at-home strategies may help control symptoms as well. Some things you can do include:4

  • Protecting your hands from the cold with gloves. This can prevent Raynaud’s phenomenon.
  • Relieving inflammation with over-the-counter drugs like ibuprofen
  • Reducing stress, since stress can make certain symptoms worse
  • Stop smoking, which can worsen some symptoms

MCTD may be a frustrating disease because it combines aspects from many disorders. However, with proper treatment, it is possible to manage MCTD and maintain a good quality of life.2

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Written by: Juliette Daly | Last reviewed: March 2021