Mutations in calreticulin have been identified as driver mutations in BCR-ABL1-negative myeloproliferative neoplasms (MPNs) and are especially important for diagnostics and prognosis in primary myelofibrosis and essential thrombocythemia. The vast majority of pathogenic variants are insertions or deletions in exon 9 that result in a mutant C-terminal sequence that activates the signaling of the thrombopoietin receptor, which in turn promotes megakaryocytic proliferation. This review examines the potential clinical utility of calreticulin mutations as laboratory biomarkers in essential thrombocythemia (ET) and primary myelofibrosis (PMF). It emphasizes their role in confirming clonality in JAK2/MPL-unmutated cases, distinguishing a clonal myeloproliferative disease from reactive thrombocytosis, clarifying the molecular interpretation, and guiding molecular diagnostic workflows. Special focus is placed on practical laboratory challenges, such as choosing assays, detecting rare and non-canonical variants in exon 9, analytical sensitivity, molecular reporting, and the integration of bone marrow morphology, cytogenetics, co-mutations, and next-generation sequencing. Overall, clinical information gained from calreticulin testing is greatest when it is used in an integrated clinicopathologic and molecular testing context rather than as a standalone test. To make calreticulin mutations more effectively used for diagnosis or prognosis in routine hematology practice, we need standardization of testing, harmonization of reporting, and prospective validation of risk-models based on both the subtypes and the burden of the mutation.

Emergency myelopoiesis in cancer and chronic inflammation leads to the accumulation of myeloid-derived suppressor cells (MDSCs) which localize at tumor sites or areas of chronic inflammation, serving as suppressor cells. Besides reducing the cytotoxic functions of T/NK cells, these cells are major players of the inflammatory process that characterizes the onset and progression of cancer. Inflammation is thought to play a relevant role in the progression of primary myelofibrosis (PMF) and recent studies reported an increased frequency of circulating polymorphonuclear MDSCs (PMN-MDSCs) in these patients, especially in an advanced disease stage. Here, we describe an involvement of the axes CXCL8-CXCR1/2 and, at a lesser extent, CXCL12-CXCR4 in the occurrence of circulating PMN-MDSCs in patients. Our data suggest that, in PMF patients, the persistent inflammatory stimulus promotes the upregulation of CXCR1 expression on PMN-MDSCs (P = 0.024) compared with healthy subjects (HDs). A similar expression of CXCR1 is observed in the circulation of HDs treated with G-CSF (G-HDs) where the egression of MDSCs is related to the chemokine CXCL8. Moreover, the protein levels of CXCR4, an important factor in recruiting MDSCs, are elevated on PMN-MDSCs from PMF (P = 0.02) and G-HDs (P = 0.03) compared to controls, a pattern previously observed in solid cancers. Interestingly, in G-HDs the mobilization of PMN-MDSCs is a consequence of G-CSF stimulation and transient, while in PMF it is possibly mediated by the chronic inflammatory status characterizing the disease. These findings indicate that the overexpression of two distinct membrane receptors plays a prominent role in the biology of MDSCs in PMF.

Connective tissue disease (CTD) is one of the common autoimmune diseases (AIDs). Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disease characterized by peripheral blood monocytosis and bone marrow dysplasia, and it is frequently associated with autoimmune complications and secondary myelofibrosis (MF). This article reports a 52-year-old male patient with recurrent arthritis and fever as the main manifestations, for whom CTD was initially considered, and who received hormone and immunosuppressant combination therapy for 2 years 10 months. The patient still suffered from recurrent fever and severe anemia; further bone marrow cytology examinations revealed abnormal bone marrow hematopoiesis, and the final diagnosis was CTD complicated with CMML and MF (MF-3 grade). After the patient was transferred to the hematology department, we adopted the azacytidine + ruxolitinib dual-target regimen to simultaneously target autoimmune inflammation, malignant clonal hematopoiesis, and severe myelofibrosis. After treatment, the patient's fever and other systemic symptoms were significantly relieved, monocytosis was corrected, and severe anemia and thrombocytopenia were markedly improved.

Patients with blast-phase (BP) myeloproliferative neoplasms have dismal outcomes, but allogeneic hematopoietic stem cell transplantation (alloHSCT) may offer a potential cure. However, the optimal pre-transplant blast-reduction therapy remains to be determined. We retrospectively analyzed outcomes in a molecularly annotated cohort of 24 patients with BP myelofibrosis (MF) who underwent alloHSCT between 2008 and 2023. Before conditioning, 20 patients received intensive induction chemotherapy, 1 received decitabine plus venetoclax, and 3 proceeded directly to transplant. At transplantation, 13 patients (54%) were in complete remission (CR), defined as bone marrow blast < 5%, or CR with incomplete count recovery (CRi), while 11 (46%) had active disease. The median follow-up was 2.9 years (range 0.02-15.5). The 3-year overall survival (OS) was 62%, progression-free survival (PFS) was 49%, relapse incidence was 38%, and non-relapse mortality was 12%. There was a trend toward better OS and PFS in patients transplanted in CR/CRi compared with those with active disease (OS 68% vs. 55%, HR 0.42, p = 0.16; PFS 61% vs. 36%, HR 0.49, p = 0.21). Mutations in TP53 and EZH2 were associated with significantly inferior PFS (HR 6.28, p = 0.008 for TP53 and HR 3.8, p = 0.04 for EZH2).Compared with a historical cohort of 50 patients transplanted during the same period for chronic-phase MF, outcomes were similar (3-year OS: 62% vs. 58%; p = 0.6181). In conclusion, our results suggest that achieving remission before alloHSCT in BP-MF is associated with favorable outcomes. The adverse impact of TP53 or EZH2 mutations supports early post-transplant strategies to prevent relapse.

Pacritinib, an inhibitor of JAK2/IRAK1/ACVR1 that is devoid of JAK1 activity, approved for treating myelofibrosis in patients with severe thrombocytopenia, carries a label warning for QT interval prolongation. To evaluate the cardiac safety of pacritinib, a randomized, placebo- and active-controlled, single-dose thorough QT (TQT) study was conducted in healthy subjects, and a dose-finding study (PAC203) was conducted in patients with myelofibrosis. In the TQT study, 42 subjects received single doses of pacritinib 400 mg, moxifloxacin 400 mg (positive control), and placebo in a crossover design. The maximal placebo-corrected change in QT interval with pacritinib was -9.7 ms (90% confidence interval: -13.4, -6.1), and all upper confidence bounds were <10 ms. A small, clinically irrelevant inverse concentration-QTc relationship was observed. No subject administered pacritinib had a QTc interval using Fridericia's formula (QTcF) >480 ms or a change from baseline in QTcF >30 ms. Moreover, in the PAC203 trial, there was no correlation between pacritinib exposure and QTcF at weeks 12 or 24. Median QTcF changes from pre-dose to 4 h post-dose were minimal (+2.7 and -0.3 ms, respectively), and no dose-response relationship was identified. These findings suggest that pacritinib exposure is unlikely to be correlated with QT prolongation.

Gecacitinib is a novel, broad-spectrum Janus kinase (JAK) inhibitor being developed for the treatment of myelofibrosis, severe alopecia areata, ankylosing spondylitis, and atopic dermatitis. This study aimed to develop population pharmacokinetic (PopPK) models for gecacitinib and its metabolites ZG0244 and ZG0245 to evaluate influential factors. Data from healthy subjects and patients across nine clinical trials were pooled. PopPK models were developed using NONMEM, and covariates of interest were tested. The PopPK structure for gecacitinib was a two-compartment model with first-order absorption and linear elimination. The metabolite ZG0244 was best described by a two-compartment model with Michaelis-Menten formation and linear elimination, while for metabolite ZG0245, it was a one-compartment model with Michaelis-Menten formation and linear elimination. Statistically significant factors affecting pharmacokinetic parameters included sex, age, indication, and co-administration with a strong CYP3A inducer or inhibitor. The effects of sex, age, and strong CYP3A inducer on exposure were limited, requiring no dose adjustment. A strong CYP3A inhibitor increased exposure by approximately 1.3-fold. The median time to reach 95% of steady-state concentration was approximately 3 days for gecacitinib and ZG0244, and approximately 7 days for ZG0245. This study developed population pharmacokinetic models for gecacitinib and its metabolites, and quantified the effects of covariates.

Progression to moderate-to-severe myelofibrosis (MF) in JAK2 V617F-positive myeloproliferative neoplasms (MPNs) is often clinically silent, and bone marrow biopsy is invasive and unsuitable for regular monitoring. In this multicentre pilot proof-of-concept study, we aimed to develop an interpretable, non-invasive model using peripheral blood parameters to detect significant fibrosis and to explore the inflammatory mechanisms involved. A total of 336 JAK2 V617F-positive MPN patients were enrolled for model training and 92 for external validation. Candidate features (blood counts, cytokines, clinical data) were screened using least absolute shrinkage and selection operator (LASSO) and Boruta algorithms. Ten machine learning methods were compared; model discrimination, calibration and clinical benefit were evaluated. Molecular validation focused on interleukin-1β (IL-1β) in Jak2V617F knock-in mice and co-culture assays. The support vector machine model yielded the best discrimination (area under the curve [AUC] = 0.916, 95% CI 0.83-0.99), good calibration and highest clinical utility. SHapley Additive exPlanations (SHAP) interpretation identified haemoglobin, IL-1β and age as the most influential features. Preclinical experiments confirmed IL-1β upregulation with fibrosis progression, reversed by ruxolitinib or pegylated interferon-α but not hydroxyurea (hydroxycarbamide). This multicentre pilot proof-of-concept study demonstrates that an interpretable blood-based tool shows preliminary accuracy for identifying moderate-to-severe MF and underscores IL-1β as a mechanistic biomarker. The data support potential utility as a complementary approach; bone marrow biopsy remains the reference standard.

Background and Objectives: Primary myelofibrosis (PMF) is a rare hematologic malignancy with non-specific symptoms, causing diagnostic delays and missed diagnoses. Automated screening in heterogeneous electronic health records (EHRs) is challenging due to class imbalance, data sparsity, and incomplete labeling. We investigated two complementary objectives: (1) developing a screening algorithm using routine EHR data to identify PMF-risk patients for hematology consultation, and (2) assessing the applicability of positive-unlabeled (PU) learning. Methods: Using EHR data from 10 Polish hospitals, we evaluated several ensemble models and found that LightGBM achieved the best performance. Results: LightGBM achieved AP 20.83% (95% CI: 19.18-24.35%), sensitivity 45.52% (95% CI: 39.48-52.72%), and precision 14.72% (95% CI: 13.80-17.01%)-substantially exceeding expected prevalence (over 340-fold enrichment). The model captured interactions among RDW and PLT parameters revealing high-risk unlabeled patients with confirmed diagnoses (n = 5) or clinical profiles resembling PMF cases (n = 31), confirming PU problem. Conclusions: Although PU methods enhanced sensitivity, they reduced precision to levels exceeding real-world healthcare capacity. Ensemble learning enables disease identification in clinical settings.

Spontaneous bacterial peritonitis (SBP) is a life-threatening infection of ascitic fluid, typically associated with cirrhosis and advanced portal hypertension, while its occurrence in non-cirrhotic portal hypertension (NCPH) is rare and often underrecognized. Primary myelofibrosis (PMF), a myeloproliferative neoplasm, may lead to NCPH through mechanisms such as hypercoagulability, extramedullary hematopoiesis, and splenomegaly-related hemodynamic changes; however, SBP in this setting is extremely uncommon. A 60-year-old woman who presented to Dr. Soetomo General Academic Hospital with progressive painful abdominal distension, fever, and bilateral lower limb edema. Laboratory evaluation revealed leukocytosis, anemia, and elevated inflammatory markers, with preserved renal and liver function. Ascitic fluid analysis demonstrated a polymorphonuclear leukocyte count of 1676 cells/mm[3]. Serologic tests for hepatitis B and C were negative, and the aspartate aminotransferase-to-platelet ratio index score was 0.4. Imaging studies showed splenomegaly and features of portal hypertension without evidence of cirrhosis or splanchnic thrombosis. PMF was confirmed by detection of the Janus kinase 2 mutation and bone marrow biopsy findings. The patient was diagnosed with SBP in the setting of NCPH secondary to PMF and was treated with intravenous cefotaxime, resulting in clinical improvement. This case highlights that SBP can occur in non-cirrhotic portal hypertension due to PMF and underscores the importance of early diagnostic paracentesis, prompt antibiotic therapy, and increased clinical vigilance in atypical presentations.