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#Tweetorial Just finished 4 weeks on the leukemia service at @UCCancerCenter. We saw a number of patients present with a new diagnosis of acute leukemia and hyperleukocytosis, our index of concern for the development of leukostasis was dependent on if they had AML or ALL.
In 1982 Lichtman et al wrote about hyperleukocytic leukemias. The leukocrit (packed WBC volume) was described in AML, ALL, and CLL. Due to the larger mean cell volume of myeloblasts, a higher leukocrit was observed in AML compared to ALL and CLL.
The pathophysiology of leukostasis is thought to be driven in part by blood viscosity. A higher leukocrit and hematocrit correlates with a higher blood viscosity.
Along w/ higher mean cell volume, myeloblasts also initiate a higher level of endothelial activation. Stucki et al (2001) wrote on the expression of adhesion molecules in myeloblasts. A relatively high expression was seen across various morphologies of myeloblasts.
The pathophysiology of leukostasis is thought to be driven by sludging of myelobasts combined with adhesion to the endothelial wall and activation. Large numbers of blasts then lead to decreased blood flow and thrombus formation within capillaries (Rollig et al, 2015)
Clinically, hyperleukocytosis is variably defined by a total leukemia cell count of >50K or >100K. 10-20% of AML patients present with hyperleukocytosis while 10-30% of ALL patients present with hyperleukocytosis.
Leukostasis is defined by clinical signs/symptoms + hyperleukocytosis. Main sites of involvement are the CNS & lungs. Neuro findings can be variable, pulm findings are typically dyspnea and hypoxia. While leukostasis is rare, AML pts are at higher risk compared to ALL pts
Management of leukostasis is a medical emergency. IV hydration to reduce blood viscosity along with cytoreduction with hydrea and/or steroids (esp if the diagnosis of AML vs ALL is still uncertain) should be the initial steps. If induction treatment can be started, it should be.
Use of leukapheresis is controversial. A meta-analysis (Oberoi et al 2014) observed that leukapheresis had no impact on early mortality, however all trials were retrospective. In general, if patients have both neurologic & respiratory symptoms, then leukoapheresis is considered.
In summary:
- Risk of leukostasis is higher in AML compared to ALL due to higher MCV and expression of adhesion molecules
-A dx of leukostasis requires hyperleukocytosis + clinical findings
- Initial management includes IV fluids and cytoreduction. Leukapheresis is controversial
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