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To the editor, 32
The optimal treatment for patients with newly diagnosed acute myeloid leukaemia (AML) who are 33 infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)/COVID-19 is unknown. 1 
We report the case of a previously fit 27-year-old male who presented with a 3-day history of fever 35
(>39 o C), swollen, erythematous elbows and no respiratory symptoms. His white blood count (WBC) 36 was 187×10 9 /L and bone marrow ( Figure 1A & 1C) examination revealed normal karyotype AML with 37 a fms related receptor tyrosine kinase 3 (FLT3) internal tandem duplication (ITD), wild-type NPM1 38 and no additional mutations on a next-generation sequencing panel. 39
Hyperleukocytosis was immediately treated with hydroxycarbamide, dexamethasone, rasburicase 40 (for tumour lysis syndrome prophylaxis), and 3 doses of 100mg/m 2 cytarabine over the first 48 hours. 41
He received antibiotics to treat febrile neutropenia and cellulitis and although he denied any 42 respiratory symptoms, a combined nasal and pharyngeal swab for SARS-CoV-2 RNA was positive. 43
Ultrasound doppler revealed a lower-limb deep vein thrombosis, bilateral upper-arm superficial 44 thrombophlebitis and coagulation markers were indicative of disseminated intravascular coagulation 45 (DIC; Figure 1B ). Given his active SARS-CoV-2 infection and the presence of a FLT3-ITD mutation, he 46 was treated with single-agent gilteritinib, an oral FLT3 inhibitor, 2 from day 3. Gilteritinib shows 47 superior efficacy to salvage chemotherapy in relapsed/refractory FLT3-mutated AML, 3 with low rates 48 of infection and early mortality, although it is not currently licensed for use in de novo AML. 49
On day 6, he became hypoxic, with hyperpyrexia, rising C-reactive protein (CRP; Figure 1B) , and a 50 high-resolution CT scan of the chest (HRCT; Figure 1D ) showed changes typical for COVID-19. He was 51 transferred to the intensive care unit on day 7 for continuous positive airway pressure (CPAP) 52 support, but deteriorated further on day 13, requiring emergency intubation due to adult respiratory 53 distress syndrome (ARDS). Dexamethasone was briefly restarted on day 14 to treat early 54 differentiation syndrome. 2 He was extubated to CPAP on day 20, however, he experienced a febrile 55 episode associated with seizures on day 22 due to Escherichia coli bacteraemia, which precipitated 56
This article is protected by copyright. All rights reserved re-intubation, vasopressor support and further antibiotics. Gilteritinib was temporarily discontinued for 7 days from day 25 ( Figure 1A ) due to biochemical features of septic shock-related 58 cardiomyopathy. 59
During the admission, the patient experienced only 5 days of severe neutropenia (<0.5×10 9 /L) and 60 17 days of thrombocytopenia (<50×10 9 /L). Post-induction bone marrow examination showed 61 morphological ( Figure 1C Induction mortality rates with intensive chemotherapy in those with hyperleukocytosis can approach 73 30% and such chemotherapy is associated with prolonged pancytopenia (often >3 weeks) and high 74 rates of severe infections. 7 We conclude that single-agent gilteritinib can be safely administered and 75 induce remission in patients presenting with de novo FLT3-ITD positive AML. Although further 76 studies are required in this setting, gilteritinib can be considered as a treatment option for patients 77 with FLT3-mutated AML and severe COVID-19, where a prolonged period of chemotherapy-induced 78 pancytopenia could adversely affect outcomes. 79