Acute Lymphoblastic Leukemia and Acute Lymphoblastic Lymphoma: Same Disease Spectrum but Two Distinct Diagnoses

The Etiologic Landscape of Lymphoproliferation in Childhood: Proposal for a Diagnostic Approach Exploring from Infections to Inborn Errors of Immunity and Metabolic Diseases

Lymphoproliferation is defined by lymphadenopathy, splenomegaly, hepatomegaly, or lymphocytic organ and tissue infiltration. The most common etiologies of lymphoproliferation are represented by infectious diseases and lymphoid malignancies. However, it is increasingly recognized that lymphoproliferative features can be the presenting sign of rare conditions, including inborn errors of immunity (IEI) and inborn errors of metabolism (IEM). Among IEI, lymphoproliferation is frequently observed in autoimmune lymphoproliferative syndrome (ALPS) and related disorders, common variable immunodeficiency (CVID), activated phosphoinositide 3-kinase δ syndrome, and Epstein-Barr virus (EBV)-related disorders. Gaucher disease and Niemann-Pick disease are the most common IEMs that can present with isolated lymphoproliferative features. Notably, other rare conditions, such as sarcoidosis, Castleman disease, systemic autoimmune diseases, and autoinflammatory disorders, should be considered in the differential diagnosis of patients with persistent lymphoproliferation when infectious and malignant diseases have been reasonably ruled out. The clinical features of lymphoproliferative diseases, as well as the associated clinical findings and data deriving from imaging and first-level laboratory investigations, could significantly help in providing the correct diagnostic suspicion for the underlying etiology. This paper reviews the most relevant diseases associated with lymphoproliferation, including infectious diseases, hematological malignancies, IEI, and IEM. Moreover, some practical indications to orient the initial diagnostic process are provided, and two diagnostic algorithms are proposed for the first-level assessment and the approach to persistent lymphoproliferation, respectively.

B-Lymphoblastic Lymphoma in Children: A Case Series From a Single Institution

BACKGROUND

Pediatric B-lymphoblastic lymphoma is an uncommon subtype of non-Hodgkin lymphoma. Studies regarding the biology, clinical course, and approach to relapse are limited.

OBSERVATIONS

We present a series of children with B-lymphoblastic lymphoma to describe the clinical course at diagnosis and relapse as well as the role of tumor cytogenetics, immunotherapy, and hematopoietic stem cell transplant.

CONCLUSIONS

The prognostic significance of cytogenetic changes in B-lymphoblastic lymphoma is not well described but may offer improved risk stratification. Immunotherapy may offer salvage options for relapsed disease and can serve as a bridge to transplant.

The Molecular and Biological Function of MEF2D in Leukemia

Myocyte enhancer factor 2 (MEF2) is a key transcription factor (TF) in skeletal, cardiac, and neural tissue development and includes four isoforms: MEF2A, MEF2B, MEF2C, and MEF2D. These isoforms significantly affect embryonic development, nervous system regulation, muscle cell differentiation, B- and T-cell development, thymocyte selection, and effects on tumorigenesis and leukemia. This chapter describes the multifaceted roles of MEF2 family proteins, covering embryonic development, nervous system regulation, and muscle cell differentiation. It further elucidates the contribution of MEF2 to various blood and immune cell functions. Specifically, in B-cell precursor acute lymphoblastic leukemia (BCP-ALL), MEF2D is aberrantly expressed and forms a fusion protein with BCL9, CSF1R, DAZAP1, HNRNPUL1, and SS18. These fusion proteins are closely related to the pathogenesis of leukemia. In addition, it specifically introduces the regulatory effect of MEF2D fusion protein on the proliferation and growth of B-cell acute lymphoblastic leukemia (B-ALL) cells. Finally, we detail the positive feedback loop between MEF2D and IRF8 that significantly promotes the progression of acute myeloid leukemia (AML) and the importance of the ZMYND8-BRD4 interaction in regulating the IRF8 and MYC transcriptional programs. The MEF2D-CEBPE axis is highlighted as a key transcriptional mechanism controlling the block of leukemic cell self-renewal and differentiation in AML. This chapter starts with the structure and function of MEF2 family proteins, specifically summarizing and analyzing the role of MEF2D in B-ALL and AML, mediating the complex molecular mechanisms of transcriptional regulation and exploring their implications for human health and disease.