Hyperleukocytosis and Leukostasis

Hyperleukocytosis is commonly defined as a WBC count in excess of 100,000 per mm3. In acute leukemia, this carries a high early mortality rate of 20–40%. Hyperleukocytosis can cause a leukostasis syndrome. What is leukostasis?

Leukostasis is the accumulation of leukemic blast cells in the capillary lumen ("Ball's Syndrome"), resulting in neurologic and pulmonary manifestations that can lead to intracranial hemorrhage and respiratory failure (JEM, InPress, online 2/23/09)