LAUSR

A 32yearold man presented with persistant asthenia, body aches and nausea one month after COVID19 infection. On examination, he had mild hepatomegaly, oedema of both legs and flat redpurple pruritic skin lesions exacerbated on the areas of pressure of the body. His blood count showed: white cell count 3.80 × 10/L, haemoglobin concentration 121 g/L and platelet count 140 × 10/L. Microscopic examination (all images MayGrünwaldGiemsa, ×100 objective) of the blood film revealed marked neutropenia (0.8 × 10/L), 26% basophils (1 × 10/L) with reduction in number of granules and vacuolated cytoplasm (upper left image) and 1% abnormal promyelocytes with bilobed nuclei (lower left image) and cytoplasm packed with redpurple granules. No Auer rods were observed. Despite the increase in Ddimers (> 4000 ng/mL), the normal prothrombin time (PT), activated partial thromboplastin time (aPTT) and fibrinogen level were not suggestive of a severe coagulopathy. Bone marrow examination showed 17% atypical basophils (upper right image, red arrow) and 33% leukaemic promyelocytes (upper right image, black arrow) including some faggot cells (lower right image, black arrow) characteristic of acute promyelocytic leukaemia (APL). Flow cytometry showed high side scatter signal with negativity for CD34 and HLADR together with strong MPO, which is typical for APL. Cytogenetic analysis revealed t(15;17)(q24;q21) and molecular analysis showed PML::RARA fusion gene. The patient was treated with a classical alltransretinoic acid (ATRA) and arsenic trioxide (ATO) combination. Skin lesions gradually regressed and basophilia normalised at d20. Complete remission was achieved and skin lesions were fully resolved at the end of induction. Basophilia is a rare finding in blood that may be associated with acute myeloid leukaemia (AML) but is very uncommon at diagnosis of APL. It is reported that basophillineage commitment in APL is associated with an increased risk of bleeding but this was not been observed in this patient. Nevertheless, these rare observations remind us that basophilia should prompt us to look for abnormal promyelocytes, especially in case with low leucocyte count when circulating leukaemic cells may be very low.