RNP Antibodies, IgG, Serum

A positive result for RNP antibodies is consistent with a connective tissue disease. Although strongly associated with connective tissue diseases, RNP antibodies are not considered a "marker" for any particular disease except in the following situation: when found in isolation (ie, dsDNA antibodies and Sm antibodies are not detectable), a positive result for RNP antibodies is consistent with the diagnosis of mixed connective tissue disease. 

What is Mixed connective tissue disease (MCTD)?

Mixed connective tissue disease (MCTD) has signs and symptoms of a combination of disorders — primarily lupus, scleroderma, and polymyositis. Many people with this uncommon disease also have Sjogren's syndrome. For this reason, mixed connective tissue disease (MCTD) is sometimes called an overlap disease. 

What are symptoms of mixed connective tissue disease?

In mixed connective tissue disease, the symptoms of the separate diseases usually don't appear all at once. Instead, they tend to occur over a number of years, which can complicate diagnosis.

Early signs and symptoms often involve the hands. Fingers might get puffy, and the fingertips become white and numb, often in response to cold exposure. In later stages, some organs — such as the lungs, heart and kidneys — can be affected.

There's no cure for mixed connective tissue disease. Treatment depends on how severe the disease is and the organs involved.

Early indications of mixed connective tissue disease can include:

→ General feeling of being unwell. This can include increased fatigue and a mild fever.

→ Cold and numb fingers or toes (Raynaud's phenomenon). In response to cold or stress, your fingers or toes might turn white and then purplish blue. After warming, the fingers or toes turn red.

→ Swollen fingers or hands. Some people have swelling of the fingers.

→ Muscle and joint pain. Joints can become inflamed, swollen and deformed, similar to what occurs with rheumatoid arthritis.

→ Rash. Red or reddish brown patches can appear over the knuckles.

What are causes of mixed connective tissue disease?

Mixed connective tissue disease is an autoimmune disorder, although the cause isn't known. In autoimmune disorders, your immune system — responsible for fighting off disease — mistakenly attacks healthy cells.

In connective tissue diseases, your immune system attacks the fibers that provide the framework and support for your body. Some people with mixed connective tissue disease have a family history of the condition. But the role of genetics in the disease remains unclear.

What are potential complications of mixed connective tissue disease?

Mixed connective tissue disease can lead to serious complications, some of which can be fatal. Complications include:

→ High blood pressure in the lungs (pulmonary hypertension). This condition is a major cause of death in people with mixed connective tissue disease.

→ Interstitial lung disease. This large group of disorders can cause scarring in your lungs, which affects your ability to breathe.

→ Heart disease. Parts of the heart can enlarge, or inflammation can occur around the heart. Heart failure can occur.

→ Kidney damage. About one-fourth of people with mixed connective tissue disease develop kidney problems, Kidney involvement is usually mild, but can lead to kidney failure.

→ Digestive tract damage. Commonly, mixed connective tissue disease affects the digestive tract. You might have abdominal pain and problems with swallowing and digesting food.

→ Anemia. About 75% of people with mixed connective tissue disease have iron deficiency anemia.

→ Tissue death. People with severe Raynaud's disease can develop gangrene in the fingers.

→ Hearing loss. In one small study, hearing loss was reported in almost half the patients with mixed connective tissuedisease. More research is needed to understand this association.

→ Nerve damage. Sjogren syndrome can affect the nerve that carries feeling from your face to your brain (trigeminal nerve). If you have trigeminal neuralgia, even mild stimulation of your face — such as from brushing your teeth or putting on makeup — can trigger a jolt of severe pain.

What are potential treatment options for mixed connective tissue disease?

The treatment options for Mixed Connective Tissue Disease (MCTD) focus on managing symptoms and preventing complications. Here is a summary of potential treatments:

→ Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): These can relieve pain and reduce inflammation in joints and muscles.

→ Corticosteroids: Medications like prednisone can help reduce inflammation, manage acute flare-ups, and control severe symptoms.

→ Antimalarial Drugs: Hydroxychloroquine, commonly used for lupus, can help with skin and joint symptoms.

→ Immunosuppressants: Drugs like methotrexate, azathioprine, or mycophenolate mofetil may be used to suppress the immune system to reduce the activity of the disease.

→ Biologics: These are newer medications that specifically target the immune response, such as TNF inhibitors or rituximab.

→ Physical Therapy: To improve muscle strength and joint function.

→ Vasodilators: For symptoms of Raynaud's phenomenon, medications that dilate blood vessels can help.

→ Lifestyle Modifications: Such as protecting hands and feet from cold, stress reduction techniques, and smoking cessation.

The choice of treatment depends on the severity of the symptoms and the organs involved. It's important for individuals with MCTD to be monitored regularly by a rheumatologist and to adjust their treatment plan as needed over time.