Syndromes of Hyperviscosity

THE use of syndromes to describe complex lists of symptoms and signs represents a convenient economy of scientific expression. The state of serum hyperviscosity, which involves spontaneous bleeding with neurologic and ocular disorders, has, as a further economy of expression, correctly been called a hyperviscosity syndrome.1 But there are other disorders in which blood is equally hyperviscous, and they are not rare. Hyperviscosity of blood may be due not only to elevated serum viscosity but also to increased numbers of cells (polycythemia or leukemia) or to increased resistance of cells to deformation (sicklemia or spherocytosis). The clinical manifestations of any . . .