Diagnosis of leukostasis is rarely made with high confidence despite characteristic clinical presentations, . In most of the cases the physician will start aggressive treatment for leukostasis when the first respiratory or neurologic symptom or sign appears in a leukemic patient with hyperleukocytosis. Pathologically, the definition of leukostasis is simpler: “the morphological evidence of intravascular accumulation of leukemic blasts occupying most or all of the vascular lumen, with or without the presence of fibrin
Ganzel, Chezi, et al. “Hyperleukocytosis, leukostasis and leukapheresis: practice management.” Blood reviews 26.3 (2012):117-122.
For clinical aspects of leukostasis, the central nervous system and lungs are the most common sites for symptomatic vascular obstruction, but effects on other organ systems can occur. The CNS symptoms of vascular obstruction may include confusion, dizziness, headache, tinnitus, blurred vision, somnolence, stupor, delirium, coma and ataxia. On examination, focal deficits may be elicited, and retinal hemorrhages may be present. CT scan or MRI of the head may reveal intracranial hemorrhage. Respiratory symptoms of vascular obstruction include dyspnea, tachypnea, and hypoxemia, with the presence of auscultatory rales. A chest X-ray or a CT scan often will show bilateral interstitial or alveolar infiltrates. It should be noted that in patients with hyperleukocytosis, failure to immediately and properly refrigerate/place on ice a blood gas sample can result in spurious hypoxemia due to “leukocyte larceny”. Rare manifestations include acute leg ischemia, renal vein thrombosis and priapism.
Due to the dismal prognosis and the high incidence of early mortality of patients with leukostasis, leukapheresis is commonly employed in cases of hyperleukocytosis with a high risk of leukostasis, even though a critical review of the available data suggests that in patients with hyperleukocytosis without leukostasis, early initiation of chemotherapy, hydroxyurea and supportive care are much more important than leukapheresis.