Reporting a case of a patient with Acute Myeloid Leukemia (AML) and increased basophils and episodes of histamine release.

Data collection in HSPE's digital system.

A 58-year-old woman, addicted, ex-smoker and ex-alcoholic complaining of fatigue, headache, visual scotomas and loss of 30 kgs who on physical examination showed dyspnea, splenomegaly and signs of retinal leukostasis. Hemoglobin 6.4 g/dL, leukocytes 312,870/mm3 (5% blasts) and platelets 186,000/mm3, LDH 4,317 U/L and uric acid 15 mg/dL. Myelogram: 21% blasts, some with metachromatic granules and 9% basophils. Normal karyotype and FISH. There was no description of basophils in immunophenotyping (IPP). It was not possible to measure serum tryptase and the PCR for BCR-ABL was negative. She had hydroxyurea and 1 session of leukapheresis. Ten days after discontinuation of the antimetabolite due to leukopenia, the patient presented with hypotension and dyspnea, responsive to volume expansion, corticosteroid therapy and broad-spectrum antibiotic therapy. Without performance status for an intensive chemotherapy regimen due to chronic obstructive pulmonary disease and karnofsky= 60%, the AZAVIT-ABCDEF protocol (azacitidine associated with erythropoietin, filgrastim with high doses of vitamins B1, C and D3) was chosen, after signing a consent form - CAAE 53015421000005463. She was discharged and returned in 15 days with leukocytosis. Cytoreduction with hydroxyurea was reinitiated. A new medullary evaluation and IPP with a panel to study basophils showed increased immature basophils. There was a drop in leucometry and 5 days after its suspension, in the absence of neutropenia, she presented with dyspnea, cough, desaturation and hypotension, responsive to volume resuscitation, corticotherapy and diphenhydramine. There was no infectious focus and cultures were negative. After this second episode, the patient is on continuously use of H1 and H2 antihistamines. She is still undergoing treatment for AML, however, the protocol has been changed for azacitidine and venetoclax, for 7 days every 28 days, due to the increase in blasts in peripheral blood. She has had 2 cycles and is now in complete remission.

However, the protocol was changed to azacitidine and venetoclax, for 7 days every 28 days, due to the increase in peripheral blood blasts, she received 2 cycles and is in complete remission. The basophilic AML classification is not standardized and the WHO classification does not specify the number of basophils. Valent et al classified basophilic leukemia in the presence of 40% of basophils, being acute if it has more than 20% of blasts. The reported case, despite not having a number of basophils above 40%, presented a typical picture of histamine release. Distinguishing the basophilic blast is difficult even with toluidine blue staining.

basophils store histamine in their granules and its degranulation can lead to serious conditions with increased vascular permeability, increased complement and release of other inflammatory cytokines. There is little information about the prognosis and survival of this subtype of AML, the patient in question has a current survival of 9 months. It is important to think about this entity when the morphology and immunophenotyping are suggestive for the treatment of histamine release to be adequate, a serious and potentially fatal situation.