An Overview of Mixed Connective Tissue Disease (MCTD)

Mixed connective tissue disease (MCTD) is an autoimmune disease that has some characteristics of three other connective tissue diseases—systemic lupus erythematosus (SLE), polymyositis, rheumatoid arthritis, Sjogren's syndrome, and scleroderma as well.

Cause

About 80 percent of people diagnosed with MCTD are women. The disease affects people between ages 5 to 80, with the highest prevalence among adolescents or people in their 20s.

The cause of MCTD is not known. There may be a genetic component, but it's not directly inherited.

Symptoms

Early effects of mixed connective tissue disease are similar to those associated with other connective tissue diseases.

Symptoms may include:

• Fatigue
• Muscle pain or weakness
• Joint pain
• Low-grade fever
• Raynaud's phenomenon

Less common effects of MCTD include a high fever, severe muscle inflammation, acute arthritis, aseptic (non-infectious) meningitis, myelitis, gangrene of the fingers or toes, abdominal pain, trigeminal neuralgia, difficulty swallowing, shortness of breath, and hearing loss.

The lungs are affected in up to 75 percent of people with MCTD. About 25 percent of those with MCTD have kidney involvement.

Diagnosis

The diagnosis of mixed connective tissue disease can be very difficult. Features of the three conditions—SLE, scleroderma, and polymyositis—typically do not occur at the same time and usually develop one after the other over time.

There are several factors that would help distinguish MCTD from SLE or scleroderma:

• High concentrations of blood anti-RNP (ribonucleoprotein) and/or anti-Smith/RNP (Sm/RNP) antibodies in the absence of lupus-specific antibodies (anti-dsDNA antibodies) or scleroderma-specific antibodies (anti-Scl-70)
• The absence of certain complications that are common with SLE, such as kidney problems and central nervous system problems
• Severe arthritis and pulmonary hypertension (neither are common in lupus)
• Severe Raynaud's phenomenon and swollen/puffy hands (neither are common with lupus)

The presence of isolated anti-RNP or anti-Sm/RNP antibodies in the blood is the primary distinguishing characteristic that lends itself to the diagnosis of MCTD, and the presence of these antibodies in the blood can actually precede symptoms.

Treatment

Treatment of MCTD is focused on controlling symptoms and managing the systemic effects of the disease, such as organ involvement.

Inflammatory symptoms may range from mild to severe, and treatment would accordingly be chosen based on the severity.

• For mild or moderate inflammation, NSAIDs or low-dose corticosteroids may be prescribed.
• Moderate to severe inflammation may require a high dose of corticosteroids.

When there is organ involvement, immunosuppressants may be prescribed. And a systemic effect like pulmonary hypertension is treated with anti-hypertensive medications.

Outlook

Even with an accurate diagnosis and appropriate treatment, the prognosis is not predictable. You can experience extended symptom-free periods, during which you might not need treatment for your MCTD.

The effect of the condition on your health depends on which organs are involved, the severity of inflammation, and the progression of your disease.

According to the Cleveland Clinic, 80 percent of people survive at least 10 years after being diagnosed with MCTD. The prognosis for MCTD tends to be worse for patients with characteristics that are tied to scleroderma or polymyositis.