This study was approved by the Institutional Review Board of Northwell Health. Table 1 summarized the clinical and laboratory findings of the three patients. Patient 1 was an 89-year-old woman who presented with persistent leukocytosis and weight loss. She was diagnosed with MDS/MPN-U on bone marrow biopsy and treated with hydroxyurea (500 mg, Oral Daily). Her hematological parameters showed progressive improvement and the response lasted about 30 months in terms of leukocytosis. During this period, she had a median white blood cell (WBC) of 20.5 x 109/L, a median hemoglobin (Hb) of 10.3 g/dL, and a median platelet of 198 x 109/L. With disease progression, her platelet count has been gradually elevated while the WBC count was relatively stable. She eventually developed significant leukocytosis (56.2 x 109/L at peak) and thrombocytosis (752 x 109/L at peak) (Fig. 1G). During the entire clinical course, her WBC ranged from 13.2 to 75.0 x 109/L, Hb from 6.7 to 11.3 g/dL, mean corpuscular volume (MCV) from 96.7 to 122.1 fl, and platelet from 67 to 752 x 109/L, and she received ten RBC transfusions. She has been hospitalized twice for a total of 26 days, which occurred within the last two months of her life. She received palliative care and died 33 months after diagnosis. Patient 2 was an 84-year-old man with multiple comorbidities. He presented with severe shortness of breath, productive cough, and had marked thrombocytopenia. Complete blood count (CBC) showed WBC of 16.2 x 109/L, Hb of 9.2 g/dL, and platelet of 32 x 109/L. There was a possibility that acute febrile condition might partly contributed to his thrombocytopenia. During the hospitalization, he received two RBC transfusions and five platelet transfusions, and became refractory to platelet transfusion. He subsequently developed sepsis and was treated with vancomycin and Zosyn. Bone marrow biopsy findings were consistent with MDS/MPN. He received supportive care and died of multiorgan failure ten days after the admission. Patient 3 was an 81-year-old man with a history of hepatitis C and cirrhosis who was admitted for leukocytosis, worsening anemia, and marked thrombocytopenia. He was diagnosed with MDS/MPN-U on bone marrow biopsy and initially treated with a hypomethylating agent. After treatment, his leukocytosis significantly improved, but anemia and thrombocytopenia persisted. During the clinical course, the WBC ranged from 2.6 to 14.6 x 109/L, Hb from 6.6 to 9.2 g/dL, platelet from 6.0 to 27.0 x 109/L. He became transfusion dependent after the diagnosis of MDS/MPN-U and received a total of nineteen RBC transfusions over the entire clinical course. He had multiple hospitalizations lasting for 43 days and the last admission was complicated by sepsis. He received palliative care and died two months after diagnosis. Splenomegaly was present only in patient 3 (19 cm in length by CT scan). Serum lactate dehydrogenase level was elevated in patient1 and patient 2.
The CBC at presentation showed a median WBC count of 16.2 x 109/L (range, 14.6-58.5), a median Hb level of 9.2 g/dL (range, 7.3-10.6), a median MCV of 99.7 fl (range, 85.5-100.4), a median corpuscular hemoglobin (MCH) of 31.6 pg (range, 28.9-32.3), and a median platelet count of 32.0 x 109/L (range, 27.0-216.0). Differential cell count revealed greater than 80% neutrophils and less than 10% immature granulocytes in all the patients. The absolute monocyte count was >1 x 109/L in two patients (patient 1, patient 2), but the monocyte percentage was only increased (10%) in patient 2. There was no increase in peripheral blood blasts, lymphocytes, or eosinophils in any of the patients. The absolute reticulocyte counts were 65.0 k/ul and 63.8 k/ul in patient 1 and patient 3, respectively.
Bone marrow biopsy showed marked hypercellularity in all the patients, including two patients with myeloid predominance and one patient with erythroid predominance (patient 2). Myelopoiesis and erythropoiesis showed normal maturation in all the patients. Megakaryocytes were normal number in two patients and markedly increased in one patient (patient 3). Multilineage dysplasia was evident in two patients while only dyserythropoiesis was present in patient 1. Bone marrow aspirate smear iron stain showed >15% ring sideroblasts in two patients (patient 1, patient 2). Other bone marrow findings included multiple lymphoid aggregates (patient 1), presence of granulomas and increased macrophages with focal hemophagocytosis (patient 2), megakaryocytosis and fibrosis (patient 3). (Fig. 1A-1F)
Immunohistochemical studies revealed bone marrow involvement by 10% B cells with SLL/CLL phenotype (patient 1), 7% CD34-positive blasts (patient 2), and significantly increased megakaryocytes (patient 3). There was no increase in CD34-positive blasts in patient 1 and patient 3.
In patient 1, flow cytometry analysis detected a minute population of monoclonal B-cells (positive for kappa, CD19, dim CD20, CD23, CD5; negative FMC-7, CD10, CD38) with SLL/CLL phenotype in both peripheral blood and bone marrow specimens. There was no increase in myeloblast or monocyte, and myeloid granularity was normal in bone marrow. In patient 2, flow cytometry of bone marrow showed increased myeloblasts (positive for partial HLA-DR, partial CD5, CD7, CD11b, partial CD13, CD33, partial CD34, partial CD117 and negative for CD2, CD3, CD4, CD56), increased monocytic cells (positive for partial HLA-DR, CD4, CD11b, heterogeneous CD13, partial CD14, CD15, CD33, CD64 and negative for CD2, CD34, CD56, CD117), and decreased myeloid granularity. The monocytic cells demonstrated an aberrant immunophenotype including partial expression of HLA-DR and heterogeneous expression of CD13. In patient 3, flow cytometry of bone marrow revealed mildly decreased myeloid granularity with no increase in blast.
Conventional cytogenetic analysis revealed a normal karyotype in patient 1 and -7/-7q abnormalities in patient 2, patient 3. FISH studies using probes for MDS panel confirmed the cytogenetic findings and showed no additional abnormalities. BCR-ABL fusion was not detected in any of the patients.
NGS studies (OnkoSight Myeloid panel comprising 37 genes, Bioreference laboratories) identified four to six somatic mutations in each of the patients (Table 2). CSF3R T618I mutation was present in all the patients with a variant allele frequency (VAF) ranging from 27% to 49%. In addition, patient 1 harbored TET2, SF3B1 and CSF3R S810Qfs* mutations; patient 2 harbored ASXL1, U2AF1, SETBP1, KRAS, and RUNX1 mutations; patient 3 harbored TET2, U2AF1, SETBP1, PTPN11, and ZRSR2 mutations. CSF3R S810Qfs*, KRAS, and PTPN11 mutations were present as subclones. NGS study was also performed in patient 1 when her CBC indices showed response to the treatment. The NGS revealed a disappearance of the CSF3R S810Qf*6 mutation, significantly decreased CSF3R T618I VAF, and a stable SF3B1 mutation.