hyperviscosity syndrome, several syndromes associated with increased thickness and slowed flow rate of blood. One type, which results from serum hyperviscosity, is caused by increased proteins and is characterized by neurologic and ocular disorders. Another type is polycythemia, causing organ congestion, reduced capillary perfusion, and increased cardiac effort. A third group includes conditions in which the deformability of erythrocytes is impaired, such as sickle cell anemia.
