LAUSR

An 18-year-old girl with a 2-month history of dizziness and fatigue was found to have a WBC of 27 54 9 10/l, a haemoglobin concentration (Hb) of 82 g/l and a platelet count of 13 9 10/l. Immunophenotyping showed 46% blast cells, which were positive for CD13, CD33, CD34, CD38, HLADR, CD117 and myeloperoxidase (MPO), but negative for lymphoid markers. On peripheral blood (PB) and bone marrow (BM) examination, some blast cells contained large colourless or pink cytoplasmic inclusions, some of which contained Auer rods (top left, PB). An MPO stain showed strong positivity of the Auer rods and as a rim around the inclusions (top right, BM). Cytogenetic study of her bone marrow cells showed 46,XX,t(7;11)(p22;q21),del(13)(q14)[7]/ 46,XX[13] and a CEBPA mutation was present. A second patient, a 48-year-old woman with a threemonth history of fever, dizziness and headache, had a WBC of 66 07 9 10/l, Hb 97 g/l and a platelet count of 53 9 10/l. Immunophenotyping showed 72% blast cells, which were positive for HLA-DR, CD7, CD13, CD33, CD34, CD38, CD58, CD117, CD123 and MPO, but negative for lymphoid markers. Similar to the first patient, cytoplasmic inclusions were present in blast cells in PB and BM, and Auer rods were present within some inclusions (bottom left, PB, and bottom right, BM. MPO stain). Cytogenetic study showed 47,XX,del(9)(q22),+r[20]. DNMT3A, PHF6, TET2, ASXL1, TP53 and WT1 mutations were present. Rare cases of acute myeloid leukaemia, myelodysplastic syndrome, chronic myeloid leukaemia and mixed phenotype acute leukaemia have cytoplasmic inclusions, referred to as a pseudo-Ch ediak-Higashi anomaly. The observation of Auer rods within such exclusions is exceptional.