Mixed Connective Tissue Disease – Symptoms and Causes
Overview
Mixed connective tissue disease (MCTD) is an uncommon condition that combines symptoms from several autoimmune disorders, primarily lupus, scleroderma, and polymyositis.
Many patients also experience signs of Sjogren’s syndrome, earning MCTD its reputation as an “overlap disease.”
The development of MCTD typically follows a gradual pattern. Symptoms don’t appear simultaneously but instead develop over several years, making diagnosis challenging.
As the disease progresses, it may impact major organs including:
- Lungs
- Heart
- Kidneys
Currently, there is no cure for mixed connective tissue disease. Treatment approaches vary based on disease severity and which organs are affected.
Symptoms
Mixed connective tissue disease (MCTD) often shows a range of symptoms that can vary from person to person. These symptoms typically develop gradually over time.
Common early signs include fatigue, a general feeling of discomfort, and swollen fingers or hands. Many people experience joint pain and muscle aches, especially in the morning.
About 75% of patients with MCTD also experience Raynaud’s phenomenon. This condition causes fingers and toes to turn white or blue when exposed to cold temperatures or during stressful situations.
Other symptoms may include:
- Skin rashes similar to those seen in lupus
- Hair loss
- Difficulty swallowing
- Shortness of breath
- Heartburn or acid reflux
- Mild fever
Swelling of the lymph nodes may occur in some cases. Some patients develop lung problems that can lead to breathing difficulties or pulmonary hypertension.
MCTD can affect the heart, causing inflammation of the heart muscle or the sac around the heart. Kidney problems are less common than in other connective tissue diseases but can still happen.
When to Get Medical Help
Contact your doctor if you notice signs that might point to mixed connective tissue disease. These include:
- Swollen, painful joints
- Ongoing finger or hand pain, especially in cold temperatures
- Unexplained muscle weakness
- Persistent fever without a clear cause
- Unusual tiredness that doesn’t improve with rest
Many symptoms of mixed connective tissue disease overlap with other conditions, so getting proper testing is important.
If you already have a diagnosis, call your doctor promptly if your symptoms worsen or if you develop new symptoms.
Causes
Mixed connective tissue disease (MCTD) develops when the body’s immune system mistakenly attacks its own tissues. Doctors don’t fully understand why this happens, but several factors likely contribute to this condition.
Genetic factors play an important role in MCTD development. People with certain genes may have a higher risk of developing this disease.
Research shows that having specific human leukocyte antigen (HLA) genes, particularly HLA-DR4, increases susceptibility.
Environmental triggers can activate the disease in genetically predisposed individuals. These triggers might include:
- Viral infections
- Exposure to certain chemicals
- Hormonal changes
- Ultraviolet light exposure
Hormonal influence may explain why MCTD affects women more often than men. The disease typically develops during a person’s 20s and 30s, with women outnumbering men by a ratio of about 8 to 1.
The immune system malfunction in MCTD causes the body to produce specific antibodies called anti-U1-RNP (anti-ribonucleoprotein) antibodies. These antibodies target healthy cells and tissues, leading to inflammation and damage in various parts of the body.
Unlike other connective tissue diseases, MCTD has a defining characteristic: nearly all patients test positive for high levels of anti-U1-RNP antibodies.
Risk Factors
Several factors may increase a person’s chance of developing mixed connective tissue disease (MCTD).
Women face a higher risk than men, with about 80% of cases occurring in females. The disease typically starts between ages 15 and 40, though it can affect people of any age.
People with family members who have autoimmune disorders may have an increased risk. However, MCTD itself is not directly inherited.
Research suggests that smoking may worsen symptoms and disease progression. Additionally, exposure to silica dust in certain occupations has been associated with an increased risk of various autoimmune disorders, including MCTD.
Complications
Mixed connective tissue disease (MCTD) can lead to several health problems if not properly managed. The overlap of different autoimmune conditions creates unique challenges for patients.
Lung problems often develop in people with MCTD. About 75% of patients experience some form of lung involvement, including pulmonary hypertension (high blood pressure in the lung arteries) and interstitial lung disease (scarring of lung tissue).
These conditions can cause breathing difficulties and reduced oxygen levels.
Heart complications may also occur. These include:
- Inflammation of the heart muscle (myocarditis)
- Abnormal heart rhythms
- Heart valve problems
- Pericarditis (inflammation of the sac around the heart)
Kidney damage happens in about 25% of MCTD cases. This typically resembles the kidney problems seen in lupus patients. Without treatment, kidney function may decline over time.
Digestive system issues are common and can affect quality of life. Many patients experience problems with swallowing, heartburn, and reduced movement of food through the digestive tract. These symptoms result from muscle weakness and tissue damage.
Nerve damage occurs in some cases. This might include:
- Numbness or tingling in hands and feet
- Nerve pain
- Reduced sensation
- Weakness in muscles
Blood vessel inflammation increases the risk of Raynaud’s phenomenon becoming severe. In extreme cases, poor circulation can lead to tissue damage and even gangrene in fingers or toes.
Pregnancy complications are more likely in women with MCTD. These include higher rates of miscarriage, premature birth, and flares of disease activity during pregnancy.
