Section 5. Bone, Joint, and Muscle Disorders

Chapter 68. Autoimmune Disorders of Connective Tissue

Topics: Introduction | Systemic Lupus Erythematosus | Scleroderma | Sjögren's Syndrome | Polymyositis and Dermatomyositis | Mixed Connective Tissue Disease | Relapsing Polychondritis | Eosinophilic Fasciitis

Mixed Connective Tissue Disease

Mixed connective tissue disease is a term used by some experts to describe a collection of symptoms similar to those of systemic lupus erythematosus, scleroderma, polymyositis, and dermatomyositis.

About 80% of people who have this disease are women. Mixed connective tissue disease affects people from ages 5 to 80. Its cause is unknown, but it appears to be an autoimmune disorder.

Symptoms

The typical symptoms are Raynaud's phenomenon (in which the fingers suddenly become very pale and tingle or become numb in response to cold or emotional upset (see Section 3, Chapter 34)), joint inflammation (arthritis), swollen hands, muscle weakness, difficulty in swallowing, heartburn, and shortness of breath. Raynaud's phenomenon may precede other symptoms by many years. Regardless of how mixed connective tissue disease starts, it tends to worsen, and symptoms spread to several parts of the body.

The hands are frequently so swollen that the fingers look like sausages. A purplish butterfly-shaped rash on the cheeks and bridge of the nose, red patches on the knuckles, a violet discoloration of the eyelids, and red spider veins on the face and hands all may appear. Skin changes similar to those in scleroderma also may occur. The hair may thin.

Almost everyone with mixed connective tissue disease has aching joints; about 75% develop the swelling and pain typical of joint inflammation (arthritis). Mixed connective tissue disease damages the muscle fibers, so the muscles may feel weak and sore, especially in the shoulders and hips.

Although the esophagus is often affected, it seldom causes difficulty in swallowing and is not painful. Fluid may collect in or around the lungs. In some people, abnormal lung function is the most serious problem, causing shortness of breath during exertion.

Occasionally, the heart is weakened, leading to heart failure (see Section 3, Chapter 25). Symptoms of heart failure may include fluid retention, shortness of breath, and fatigue. The kidneys and nerves are affected in only 10% of people, and the damage is usually mild compared to the damage caused by lupus. Other symptoms may include a fever, swollen lymph nodes, abdominal pain, and persistent hoarseness. Sjögren's syndrome may develop. Over time, most people develop symptoms that are more typical of lupus or scleroderma.

Diagnosis and Treatment

Doctors suspect mixed connective tissue disease when some symptoms from lupus, scleroderma, polymyositis, or rheumatoid arthritis overlap.

Blood tests are performed to detect an antibody to ribonucleoprotein, which is present in almost all people who have mixed connective tissue disease. A high level of this antibody without the other antibodies present in lupus is reasonably specific for mixed connective tissue disease.

The treatment is similar to that of lupus. Corticosteroids are usually effective, especially when the disease is diagnosed early. Mild cases can be treated with aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs), quinacrine or similar drugs, or very low doses of corticosteroids. The more severe the disease, the higher the dose of corticosteroid needed. In severe cases, immunosuppressive drugs may also be needed.

In general, the more advanced the disease and the greater the organ damage, the less effective the treatment. Scleroderma-like damage to the skin and esophagus is least likely to respond to treatment. Symptom-free periods can last for many years with little or no continuing treatment with a corticosteroid. Despite treatment, mixed connective tissue disease progresses in about 13% of the people, producing potentially fatal complications in 6 to 12 years.