This case series summarizes the clinical, laboratory, molecular genetic features and treatment outcomes of pediatric B-cell acute lymphoblastic leukemia (B-ALL) with myocyte enhancer factor 2D (MEF2D) gene rearrangement. The goal was to characterize presentation, immunophenotype, fusion partners, concurrent genetic alterations, response to standardized induction therapy, and subsequent clinical course in children treated at a single center.
Clinical data were collected for 9 children newly diagnosed with B-ALL harboring MEF2D gene rearrangements who were admitted to the First Affiliated Hospital of Zhengzhou University from May 2020 to June 2025. The investigators systematically reviewed demographic information, presenting symptoms, immunophenotyping, bone marrow morphology, RNA sequencing results for fusion partners, detection of copy number changes, treatment regimens, minimal residual disease (MRD) status by flow cytometry at the end of induction, and follow-up outcomes through October 10, 2025.
All patients received induction therapy following the Clinical Practice Guideline for Childhood Acute Lymphoblastic Leukemia (2018) using the VDLP regimen (vincristine, daunorubicin, L-asparaginase, prednisone). Specific laboratory platforms and sequencing methods were reported in the source as RNA sequencing for fusion detection; additional methodological details were not provided in the abstract.
Nine children were included (3 boys, 6 girls). The diagnostic age distribution had a median of 12.0 years with an interquartile range of 11.0 to 13.8 years, indicating this subtype is more common in older pediatric patients. Five of the nine children initially presented with fever accompanied by arthralgia.
Immunophenotyping classified 1 child as early precursor B-ALL and the remaining 8 as common B-ALL. A consistent immunophenotypic pattern across all nine cases was described: uniformly high expression of CD38 and absence of cytoplasmic immunoglobulin M (cIgM). These markers were emphasized as characteristic features in the reported cohort.
Bone marrow smear examination identified cytoplasmic vacuolization in 5 of the 9 children. No additional morphological details or quantitative blast percentages were reported in the abstract.
RNA sequencing identified five distinct MEF2D fusion partners among the 9 patients: BCL9 (4 cases), FOXJ2 (2 cases), and single cases with DAZAP1, SS18, and ARNT fusion partners. Copy number analysis detected heterozygous deletions of CDKN2A or CDKN2B in 6 children. Overall, 8 of the 9 children had concurrent gene variations in addition to the MEF2D fusion. The abstract does not provide a full list of all concurrent variants or their functional annotations.
All nine children received induction therapy with the VDLP regimen (vincristine, daunorubicin, L-asparaginase, prednisone) in accordance with the 2018 national guideline for childhood ALL. At the end of induction remission therapy, MRD assessed by flow cytometry was negative (<0.01%) in all cases, indicating a uniformly favorable early treatment response by this metric.
Follow-up status was reported through October 10, 2025. One patient was lost to follow-up during the maintenance phase. Three children experienced relapse and subsequently died. Of the remaining patients, two were reported as disease-free survival at last follow-up, and three were still receiving regular treatment. These results indicate that despite an initially excellent MRD response, relapse occurred in a notable proportion of this small cohort and salvage treatment outcomes were limited.
In this single-center series of nine pediatric patients, B-ALL with MEF2D gene rearrangement predominated in older children and commonly presented with fever and arthralgia. The cohort demonstrated a characteristic immunophenotype of high CD38 expression and absent cIgM. Molecular profiling revealed diverse fusion partners with MEF2D, most frequently BCL9, and a high incidence of heterozygous CDKN2A/CDKN2B deletions. Although induction therapy per guideline produced negative flow cytometry MRD in all patients, relapse risk remained high and salvage therapy yielded limited success in those who relapsed.
The authors suggest that for this high-risk subtype, employing next-generation sequencing–based MRD monitoring might offer more precise relapse risk assessment than flow cytometry alone. This recommendation reflects the discordance observed between early MRD negativity and subsequent relapses in the cohort.
Details not reported in the abstract include full sequencing methodology, the complete list and functional significance of concurrent gene variants, blast percentages and other morphological metrics, specifics of relapse treatments or salvage regimens, duration of follow-up for each patient, and statistical analysis. The study is a small single-center case series (n=9), which limits generalizability and precludes estimation of incidence or robust prognostic stratification.