Extreme leukemic leukocytosis (blast crisis) in childhood.

Children with leukemia who have extremely high leukocyte counts (more than 100,000/mm3) when seen initially are at high risk of early sudden death, usually from massive intracerebral hemorrhage. Nine such patients were seen during a 39-month period. Eight had pronounced adenopathy and hepatosplenomegaly without severe anemia or thrombocytopenia. The first six patients died suddenly. Cerebral perivascular infiltration and increased blood viscosity are the probable pathophysiologic mechanisms. A treatment program was developed, the goal being the early elimination of blast cells. Three consecutive patients patients presenting with leukocyte counts greater than 100,000/mm3 were treated with emergency cranial irradiation, and all three survived to receive systemic chemotherapy.