Interlude

While not primarily a chest disease, Osler Weber Rendu (OWR, otherwise known as hereditary hemorrhagic telangiectasia) is a rare genetic condition of the arteries that may manifest anywhere in the body. In this disorder, the switch that controls blood vessel growth cannot spontaneously turn off. Abnormal clusters and knots of vessels form. People with this condition often have small blood vessel malformations that cause red or purple spots on the lips or tongue. These are telangiectasia, sometimes known as birthmarks, and are commonly seen in other conditions.

The walls of the abnormal vessels are thin, weak, and fragile, and easily bleed after minor trauma. Internal blood pressure may make them blow up like a small balloon, known as an aneurysm.

Millions of fine capillaries in normal lungs act to filter out any blood clots that may arise in the body. In OWR, abnormal connections can also occur between arteries and veins that allow blood to shunt from one to the other. In this way, blood clots normally filtered in the lungs may cross over into the arterial system. Blood flow then sweeps them along to lodge elsewhere in the body, including the brain where they block an artery causing a stroke.

The chest X-ray in [Fig. 1] comes from a person with this condition. I have retained quite a lot of the original X-ray in the picture, and the complex blood vessels remain visible. People may carry the gene for the condition and never express it, and so it is impossible to know who carries this. I have therefore included several people in a crowd to represent the random nature of genetic conditions generally, and in the background, complex pipework in a factory with valves and dials represent the arteries and veins of the body.