A rare KMT2A::CBL transcript in an acute monoblastic leukemia patient with an unfavorable outcome

BACKGROUND

Lysine [K] methyltransferase 2A (KMT2A, previously known as MLL) gene rearrangements are common in acute leukemias of various lineages and are associated with features such as chemotherapy resistance and rapid relapse. KMT2A::CBL is a rare fusion of unknown pathogenesis generated by a unique interstitial deletion of chromosome 11 that has been reported across a wide age range in both acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) patients. The leukemogenic effect of the KMT2A::CBL rearrangement and its association with clinical prognosis have not been well clarified.

METHODS AND RESULTS

We report the case of a 64-year-old female who was diagnosed with acute monoblastic leukemia (M5a) and who acquired the rare KMT2A::CBL fusion. The patient received multiple cycles of therapy but did not achieve remission and eventually succumbed to severe infection and disease progression. Additionally, we characterized the predicted KMT2A-CBL protein structure in this case to reveal the underlying leukemogenic mechanisms and summarized reported cases of hematological malignancies with KMT2A::CBL fusion to investigate the correlation of gene rearrangements with clinical outcomes.

CONCLUSIONS

This report provides novel insights into the leukemogenic potential of the KMT2A::CBL rearrangement and the correlation between gene rearrangements and clinical outcomes.

A Rare Case of Cutaneous T-Cell Lymphoma Accompanied by Acute Monoblastic Leukemia and Diffuse Large B-Cell Lymphoma

A 70-year-old female was referred for brown-to-gray colored papules and nodules on her lower legs. She had been diagnosed with diffuse large B-cell lymphoma (DLBCL) in her stomach, and myelodysplastic syndrome (MDS) by bone marrow biopsy. Three years after complete remission of DLBCL, she experienced DLBCL recurrence in her small bowel and was hospitalized. MDS had been stationary, but during the treatment of DLBCL, her laboratory findings suggested signs of leukemia. Bone marrow biopsy was done, and acute monoblastic leukemia (AMoL) was diagnosed. After 1 cycle of chemotherapy for AMoL, skin lesions developed, and her skin biopsy showed cutaneous T-cell lymphoma (CTCL). Terminal deoxynucleotidyl transferase staining and CD123 staining were negative, and bone marrow re-biopsy conducted after the skin lesion developed still showed monoblastic proliferation. Whether the CTCL represented with an AMoL lineage switch could not be completely proved due to the absence of molecular or clonal marker evaluations, but the possibility of coexistence of three different malignancies was higher. During treatment, a neutropenic fever developed, and the patient died due to sepsis. We herein report a rare case of CTCL accompanied by AmoL and DLBCL.

[Pulmonary infiltration of acute monoblastic leukemia diagnosed by transbronchial lung biopsy]

A 65-year-old woman was urgently admitted to our hospital for antibiotic-resistant fever, hypoxemia, and hyperleukocytosis and was diagnosed with acute monoblastic leukemia. Chest computed tomography revealed interlobular septal thickening, central ground-glass opacity, and a nodular shadow in the left lower lobe. Although several treatments for infectious disease and acute heart failure were administered, they were less effective. Transbronchial lung biopsy was performed on day 7 of hospitalization, and subsequently, pulmonary leukemic infiltration was confirmed. Based on the diagnosis, we decided to start intensive chemotherapy. Consequently, the abnormal lung shadow on computed tomography vanished, and complete hematological remission was achieved. Although acute myeloid leukemia is frequently associated with lung infiltration during onset, it is often difficult to distinguish it from other pulmonary complications. In clinical practice, intensive chemotherapy is often initiated based on the clinical evaluation without pathological confirmation of the lung disease. Our patient was accurately diagnosed based on the pulmonary leukemic infiltration observed pathologically and recovered well. Here we report our case along with a discussion of the relevant literature.