Diagnosing Mixed Connective Tissue Disease (MCTD)

What is mixed connective tissue disease (MCTD)?

Mixed connective tissue disease (MCTD) is a rare autoimmune condition; it is often referred to as an overlap disease because the symptoms of MCTD overlap with other connective tissue conditions, including polymyositis, scleroderma and systemic lupus erythematosus (SLE). In some cases, MCTD also mimics symptoms of rheumatoid arthritis.

Autoimmune diseases develop when the immune system mistakenly attacks healthy cells; mixed connective tissue disease occurs when the immune system attacks the fibers that support the framework of the body. An estimated 25% of individuals with a connective tissue disease develop another connective tissue condition over the course of several years.

How is mixed connective tissue disease diagnosed?

Mixed connective tissue disease can be difficult to diagnose due to its resemblance to other connective tissue conditions, such as polymyositis, scleroderma and systemic lupus erythematosus (SLE). It can also co-occur with these and other connective tissue conditions, which can make diagnosis difficult.

The diagnostic process may include the following:

• A health care professional will conduct a physical exam to check for swollen, painful hands and joints.
• A detailed health history will be obtained. A written log of symptoms, duration of symptoms and frequency of symptoms is helpful in determining a MCTD diagnosis.
• If MCTD is suspected, a blood test will be ordered to check for inflammatory markers and certain antibodies, such as anti-RNP. A blood test will also determine if antibodies associated with other autoimmune diseases are present to ensure a proper diagnosis.

Differentiating factors

Certain factors can help differentiate mixed connective tissue disease from other connective tissue disorders:

• Severe kidney and central nervous system issues found in SLE are not present with MCTD.
• Severe arthritis and pulmonary hypertension are not symptoms of SLE or scleroderma; however, they are often present with MCTD.
• High concentrations of anti-RNP is associated with MCTD.
• Raynaud’s phenomenon — characterized by cold and numb fingers or toes that may become blue, white or purple due to reduced blood flow from stress or cold — occurs in only 25% of individuals with SLE and up to 90% of individuals with MCTD.