Early detection of meningeal localization in acute promyelocytic leukaemia patients with high presenting leucocyte count

Summary. Extramedullary relapse occurs infrequently in acute promyelocytic leukaemia (APL) but has been increasingly reported after the advent of all-trans retinoic acid (ATRA) treatment, probably as a consequence of improved patient survival. We describe our single centre experience of six APL patients who had disease localization in the central nervous system (CNS). In three patients, clinical symptoms (headache and/or nausea) that presented during follow-up led to the performance of a lumbar puncture and detection of overt CNS infiltration. Two of these patients had simultaneous haematological relapse and one was in molecular remission when CNS leukaemia was documented. One patient with no local symptoms showed CNS infiltration at the time of molecular relapse. Following the introduction of routine lumbar puncture, carried out after front-line induction in all newly diagnosed patients with white blood cell count (WBC) greater than 10 × 10⁹/l, two additional patients in molecular remission with no local symptoms were found to have initial APL localization in the CNS. Presenting features included in 6/6 patients an elevated WBC count (> 10 × 10⁹/l) and a predominance of the PML/RAR bcr3 type (5/6 patients) and of microgranular morphology (5/6 patients). Our findings highlight the importance of carrying out lumbar puncture in APL patients presenting with high-risk features.