Hyperleukocytosis and leukostasis: management of a medical emergency.

INTRODUCTION: Hyperleukocytosis is defined as a white blood cell count greater than 100,000/mL in patients affected by acute leukemia and often it is associated with increased morbidity and mortality, that can be up to 40% if unrecognized. Areas covered: Risk factors include younger age, myelomonocytic or monocytic/monoblastic morphology, microgranular variant of acute promyelocitic leukemia and T-cell ALL, and some cytogenetic abnormalities. Poor prognosis due to high early death rate secondary to leukostasis. The mechanisms at the origin of leukostasis are still poorly understood. The management of acute hyperleukocytosis and leukostasis involves supportive measures and reducing the number of circulating leukemic blast cells, with careful monitoring of fluid balance, control of uric acid production and control of urine pH to prevent tumour lysis syndrome. Expert commentary: Several studies have been performed to ameliorate the outcome of this setting of patients. The high number of leukocytes may cause 3 main complications: disseminated intravascular coagulation (DIC), tumor lysis syndrome (TLS), and leukostasis. Although hyperleukocytosis and tumour lysis syndrome are still a challenge for clinicians, a better prognosis for these conditions is emerging in the last years.