Acute promyelocytic leukaemia

Synopsis

Treat suspected acute promyelocytic leukaemia as a haemorrhagic emergency, confirm PML::RARA rapidly and deliver risk-adapted differentiation therapy with coagulopathy and differentiation-syndrome control.

• APL is the acute leukaemia where treatment begins on morphological suspicion: give ATRA immediately and stop it later if genetics excludes the diagnosis.
• Confirm with urgent PML::RARA RT-PCR or FISH; conventional karyotyping is useful but is too slow as the only first-hour test.
• Monitor platelets, PT, APTT and fibrinogen at least every 6 hours initially and transfuse actively to the centre target, commonly platelets above 30–50 × 10⁹/L and fibrinogen above 1.5 g/L.
• Avoid lumbar puncture, central line placement, bronchoscopy and other invasive procedures until coagulopathy is controlled unless life-saving access or intervention is unavoidable.
• Do not use leukapheresis for hyperleukocytic APL because manipulation can worsen coagulopathy and early mortality; use protocol cytoreduction.
• Low-to-intermediate-risk newly diagnosed APL, defined by WBC 10 × 10⁹/L or below, can receive ATRA plus arsenic trioxide without conventional chemotherapy under specialist protocol.
• High-risk APL has WBC above 10 × 10⁹/L and needs ATRA plus arsenic or chemotherapy with prompt protocol cytoreduction and enhanced differentiation-syndrome prevention.
• At the first suspicion of differentiation syndrome give dexamethasone 10 mg IV every 12 hours; withhold ATRA or arsenic only for severe syndrome under the protocol.
• Arsenic requires baseline and frequent ECG, potassium, magnesium, calcium, liver and renal monitoring; correct potassium above 4 mmol/L and magnesium above 0.7 mmol/L and avoid QT-prolonging combinations.
• Molecular PML::RARA monitoring defines remission and detects relapse; morphological improvement cannot substitute for protocol molecular assessment.