This week, I was called to evaluate a young man with several aneurysms (ballooning of his blood vessels) and a dilated (widened) aorta. The medical team thought he had a “connective tissue disease” because a family member also had a connective tissue disease–she had lupus. Unfortunately, doctors can mean very different things when they talk about a “connective tissue disease;” this is a common source of confusion for doctors and patients alike. After reading this post, I hope you’ll be able understand the difference.
Connective tissue is the “stuff” that holds your body together. That is, the bones, ligaments, tendons, cartilage, fat, and “glue” that keeps all your organs in place. Two very different types of diseases can affect these tissues–you can have problems in MAKING the connective tissues, or these tissues can be ATTACKED by the body’s own immune system.
In the first type of “connective tissue disease,” the body is unable to produce strong connective tissues. It’s like trying to build a house with weak materials. If the materials are weak, the house is likely to develop cracks on the walls, holes in the roof, and the whole structure may fall down. There are many genetic (heritable) diseases that prevent the body from making high-quality building blocks. Marfan syndrome, for example, is a disease where the body is unable to make high-quality fibrillin (a protein present in many types of connective tissues). This causes weakness of various parts of the body including the eye (causing lens dislocation), the aorta (causing dilation and potential to rupture), and lungs (causing pneumothorax, or collapse of a lung). Ehlers-Danlos is another group of diseases where patients have difficulties making collagen, another protein necessary for high-quality connective tissues. In this disease, patients have loose joints that often dislocate, fragile skin that is unusually “stretchy,” and have difficulties healing after injuries. In the most severe cases of Ehlers-Danlos, the blood vessels are also weak, making them prone to breaking and causing internal bleeding. Because these types of connective tissue diseases are genetic (hereditary), medical geneticists are the experts in this field.
The second type of “connective tissue disease” does not involve problems in making the building blocks of the body. In fact, the body is able to make all of the connective tissues without a problem. However, once these tissues are made, they are attacked by the body’s own immune system (and thus they are autoimmune diseases). The body’s own immune cells (white blood cells) are tricked into thinking that the connective tissue is abnormal, and thus they attacking those tissues. In a sense, the body can build a house with high-quality materials, but the house is invaded by wild animals that can damage the structure of the house. In Sjogren syndrome, for example, the glands that make tears and saliva are attacked. In scleroderma, the skin and internal organs are attacked. In lupus, many organs can be attacked, including the kidneys, skin, and lung. To date, we have very little idea what causes these diseases. Because these types of diseases are autoimmune and often involve inflammation, rheumatologists are the experts in these types of illnesses.
Don’t you think we should change the name that we use to refer to these two very different types of diseases? What names do you propose?
After reading this post, what kind of disease do you think my patient had? Genetic or autoimmune?