Leucostasis

Term is applied both to organ damage due to 'sludging' of leucocytes in the capillaries of a patient with high circulating blast count and to the lodging and growth of leukaemic blasts, usually in AML, in the vascular tree eroding the vessel wall and producing tumours and haemorrhage.

Features

• More common in AML and blast crisis of CML.

• Leucostatic tumours are associated with an exponential increase in blasts in the peripheral blood and, prior to the development of effective chemotherapy, haemorrhage from intracerebral tumours was not an uncommon cause of death.

• Pulmonary or cerebral leucostasis are serious complications which may occur in patients who present with a blast count >50 x 109/L.

• Leucocyte thrombi may cause plugging of pulmonary or cerebral capillaries. Vascular rupture and tissue infiltration may occur.

• Less common manifestations are priapism and vascular insufficiency.

• Pulmonary leucostasis causes progressive dyspnoea of sudden onset associated with fever, tachypnoea, hypoxaemia, diffuse crepitations and a diffuse interstitial infiltrate on CXR.

• Pulmonary haemorrhage and haemoptysis may occur. More common with monocytic leukaemias and the microgranular variant of acute promyelocyte leukaemia. Differentiation from bacterial or fungal pneumonia may be difficult.

• Cerebral leucostasis may cause a variety of neurological abnormalities.

• Anaemia may protect a patient with marked leucocytosis from the effects of increased whole blood viscosity. Transfusion of RBCs to correct anaemia prior to chemotherapy may initiate leucostasis.

528 Management

Urgent leucapheresis is required for a patient with marked leucostasis (>200x 109/L) or in any patient in whom leucostasis is suspected. Chemotherapy may be commenced concomitantly to further reduce the leucocyte count but may be associated with a high incidence of pulmonary and CNS haemorrhage.

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