Systemic amyloidosis is a rare disease caused by the buildup of an abnormal protein substance called amyloid in body tissues. Amyloidosis can affect many organs of the body, but involvement of the heart and blood vessels is the most common cause of illness and death in patients with this disease. In patients whose heart and blood vessels are affected by amyloidosis, shortness of breath, leg swelling, or abnormal heart rhythms are usually the first signs that they have this disease. Angina pectoris (chest pain) has not been thought of as a sign of amyloidosis.