Connective Tissue Disease

Connective tissue disease refers to a group of disorders involving the protein-rich tissue that supports organs and other parts of the body. Examples of connective tissue are fat, bone, and cartilage. These diseases often involve the joints, muscles, and skin, but they can also involve other organs and organ systems including the eyes, heart, lungs, kidneys, gastrointestinal tract, and blood vessels.

There are more than 200 disorders that affect the connective tissue.

Causes and specific symptoms vary by the different types.

Inherited Disorders of Connective Tissue

Some connective tissue diseases -- often called heritable disorders of connective tissue (HDCTs) -- are the result of changes in certain genes. Many of these are quite rare. Following are some of the more common ones.

Ehlers-Danlos syndrome (EDS). Actually a group of more than 10 disorders, EDS is characterized by over-flexible joints, stretchy skin, and abnormal growth of scar tissue. Symptoms can range from mild to disabling. Depending on the specific form of EDS, other symptoms may include:

• A curved spine
• Weak blood vessels
• Bleeding gums
• Problems with the lungs, heart valves, or digestion

Epidermolysis bullosa (EB). People with EB have skin that is so fragile that it tears or blisters as a result of a minor bump, stumble, or even friction from clothing. Some forms of EB may involve the digestive tract, the respiratory tract, the muscles, or the bladder. Caused by defects of several proteins in the skin, EB is usually evident at birth.

Marfan syndrome. Marfan syndrome affects the bones, eyes, heart, and blood vessels. People with Marfan syndrome tend to be tall and have extremely long bones and thin "spider-like" fingers and toes. Other problems may include eye problems due to abnormal placement of the eye lens and enlargement of the aorta (the largest artery in the body), which can lead to a fatal rupture. Marfan syndrome is caused by mutations in the gene that regulates the structure of a protein called fibrillin-1.

Osteogenesis imperfecta. Osteogenesis imperfecta is a condition of brittle bones, low muscle mass, and lax joints and ligaments. There are several types of this condition. Specific symptoms depend on the specific type and may include:

• Blue or gray tint to the whites of the eyes
• Thin skin
• Curved spine
• Breathing problems
• Hearing loss
• Teeth that break easily

The disease occurs when a mutation in two genes responsible for type 1 collagen reduces the amount or quality of the protein. Type 1 collagen is important to the structure of bone and skin.

Autoimmune Diseases

For other forms of connective tissue disease the cause is not known. In some cases, researchers believe they may be triggered by something in the environment of people who may be genetically susceptible. In these diseases, the body's normally protective immune system produces antibodies that attack the body's own tissues.