Eighteen patients developed severe vein narrowing. Some patients with narrowing noticed symptoms that included shortness of breath, cough, chest pain, or coughing up blood. Half of the affected patients had an abnormal chest x-ray, but the abnormalities were frequently misdiagnosed as pneumonia, lung cancer, or blood clots in the lung and incorrect treatment was often given. Correct treatment, which consisted of opening the narrowed veins, led to immediate improvement in most of the patients.