Pharmacogenomics, Race, and Treatment Outcome in Pediatric Acute Myeloid Leukemia.

Importance: Disparities in outcomes exist between Black and White patients with acute myeloid leukemia (AML), with Black patients experiencing poorer prognosis compared with their White counterparts. Objective: To assess whether varying intensity of induction therapy to treat pediatric AML is associated with reduced disparities in treatment outcome by race. Design, Setting, and Participants: A comparative effectiveness analysis was conducted of 86 Black and 359 White patients with newly diagnosed AML who were enrolled in the AML02 trial from 2002 to 2008 or the AML08 trial from 2008 to 2017. Statistical analysis was conducted from July 2023 through January 2024. Interventions: Patients in AML02 were randomly assigned to receive standard low-dose cytarabine-based induction therapy or augmented high-dose cytarabine-based induction therapy, whereas patients in AML08 received high-dose cytarabine-based therapy. Main Outcomes and Measures: Cytarabine pharmacogenomic 10-single-nucleotide variant (ACS10) scores were evaluated for association with outcome according to race and treatment arm. Results: This analysis included 86 Black patients (mean [SD] age, 8.8 [6.5] years; 54 boys [62.8%]; mean [SD] leukocyte count, 52 600 [74 000] cells/µL) and 359 White patients (mean [SD] age, 9.1 [6.2] years; 189 boys [52.6%]; mean [SD] leukocyte count, 54 500 [91 800] cells/µL); 70 individuals with other or unknown racial and ethnic backgrounds were not included. Among all patients without core binding factor AML who received standard induction therapy, Black patients had significantly worse outcomes compared with White patients (5-year event-free survival rate, 25% [95% CI, 9%-67%] compared with 56% [95% CI, 46%-70%]; P = .03). By contrast, among all patients who received augmented induction therapy, there were no differences in outcome according to race (5-year event-free survival rate, Black patients, 50% [95% CI, 38%-67%]; White patients, 48% [95% CI, 42%-55%]; P = .78). Among patients who received standard induction therapy, those with low ACS10 scores had a significantly worse 5-year event-free survival rate compared with those with high scores (42.4% [95% CI, 25.6%-59.3%] and 70.0% [95% CI, 56.6%-83.1%]; P = .004); however, among patients who received augmented induction therapy, there were no differences in 5-year event-free survival rates according to ACS10 score (low score, 60.6% [95% CI, 50.9%-70.2%] and high score, 54.8% [95% CI, 47.1%-62.5%]; P = .43). Conclusions and Relevance: In this comparative effectiveness study of pediatric patients with AML treated in 2 consecutive clinical trials, Black patients had worse outcomes compared with White patients after treatment with standard induction therapy, but this disparity was eliminated by treatment with augmented induction therapy. When accounting for ACS10 scores, no outcome disparities were seen between Black and White patients. Our results suggest that using pharmacogenomics parameters to tailor induction regimens for both Black and White patients may narrow the racial disparity gap in patients with AML.

The added value of skeletal surveys in the initial evaluation of children diagnosed with Langerhans cell histiocytosis in the era of staging 18 F-FDG PET/CT: A retrospective study.

OBJECTIVE: Currently, there is no consensus protocol on the initial staging evaluation for Langerhans cell histiocytosis (LCH). Our institutional protocol consists of a skeletal survey and a whole-body positron emission tomography with 2-deoxy-2-[fluorine-18] fluoro-D-glucose integrated with computed tomography (FDG PET/CT) study. The utility of the PET/CT lies in its sensitivity in detecting osseous and extra-osseous lesions, and in determining the baseline metabolic activity of LCH lesions to assess treatment response. However, the added utility of the skeletal survey in staging LCH is unclear. Therefore, this study retrospectively assessed the added diagnostic value of skeletal surveys in patients with baseline PET/CTs for initial staging of LCH. METHODS: We retrospectively searched the medical records of all patients less than or equal to 18 years old at a large children's hospital (May 2013 to September 2021). The inclusion criteria were (a) biopsy-proven diagnosis of LCH and (b) initial staging PET/CT and skeletal survey performed less than or equal to 1 month apart. A blinded pediatric radiologist reviewed the skeletal surveys and another reviewed the PET/CTs in identifying LCH osseous lesions. RESULTS: Our study cohort consisted of 49 children with 86 LCH osseous lesions. In non-extremity locations, PET/CT identified 70/70 (100%) osseous lesions, while skeletal surveys detected 43/70 (61.4%) osseous lesions. In the extremities, PET/CT identified 13/16 (81.3%) osseous lesions, while skeletal surveys detected 15/16 (93.8%) osseous lesions. CONCLUSION: Skeletal surveys increased the detection rate of osseous lesions in the extremities, but added no diagnostic value to the detection of osseous lesions in non-extremity locations. Therefore, we propose to abbreviate the skeletal survey to include only extremity radiographs.

Pediatric leukemia cutis: A case series.

BACKGROUND: Pediatric leukemia cutis (LC) is often difficult to diagnose due to similarity in appearance to other dermatologic diseases. Several case reports and smaller case series have been published in the medical literature, but studies on larger cohorts of children with LC are lacking. OBJECTIVE: This study aimed to better characterize the clinical features, course, and prognosis of LC in the pediatric population. METHODS: We performed a retrospective case series of 31 patients diagnosed with LC at Boston Children's Hospital and the Children's Hospital of Philadelphia. RESULTS: The number and morphology of LC lesions varied among patients, with the head and lower extremities being the most common sites of involvement. Leukemia cutis presented concomitantly with systemic leukemia in the majority of cases. Most cases of LC arose during initial leukemia episodes, rather than with relapsed leukemia. Acute myeloid leukemia was the subtype most frequently associated with LC, followed by acute lymphoblastic leukemia. Diagnosis altered treatment timing and therapeutic decisions. CONCLUSION: Children most often present concomitantly with LC and systemic leukemia. Since the morphology and distribution of LC varies, physicians must maintain a high index of suspicion for this diagnosis, as the presence of LC may change the management of systemic leukemia.

Pediatric CNS-isolated hemophagocytic lymphohistiocytosis.

Objective: To highlight a novel, treatable syndrome, we report 4 patients with CNS-isolated inflammation associated with familial hemophagocytic lymphohistiocytosis (FHL) gene mutations (CNS-FHL). Methods: Retrospective chart review. Results: Patients with CNS-FHL are characterized by chronic inflammation restricted to the CNS that is not attributable to any previously described neuroinflammatory etiology and have germline mutations in known FHL-associated genes with no signs of systemic inflammation. Hematopoietic stem cell transplantation (HCT) can be well tolerated and effective in achieving or maintaining disease remission in patients with CNS-FHL. Conclusions: Early and accurate diagnosis followed by treatment with HCT can reduce morbidity and mortality in CNS-FHL, a novel, treatable syndrome. Classification of evidence: This study provides Class IV evidence that HCT is well tolerated and effective in treating CNS-FHL.

Calm in the midst of cytokine storm: a collaborative approach to the diagnosis and treatment of hemophagocytic lymphohistiocytosis and macrophage activation syndrome.

BACKGROUND: Hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) were historically thought to be distinct entities, often managed in isolation. In fact, these conditions are closely related. A collaborative approach, which incorporates expertise from subspecialties that previously treated HLH/MAS independently, is needed. We leveraged quality improvement (QI) techniques in the form of an Evidence-Based Guideline (EBG) to build consensus across disciplines on the diagnosis and treatment of HLH/MAS. METHODS: A multidisciplinary work group was convened that met monthly to develop the HLH/MAS EBG. Literature review and expert opinion were used to develop a management strategy for HLH/MAS. The EBG was implemented, and quality metrics were selected to monitor outcomes. RESULTS: An HLH/MAS clinical team was formed with representatives from subspecialties involved in the care of patients with HLH/MAS. Broad entry criteria for the HLH/MAS EBG were established and included fever and ferritin ≥500 ng/mL. The rheumatology team was identified as the "gate-keeper," charged with overseeing the diagnostic evaluation recommended in the EBG. First-line medications were recommended based on the acuity of illness and risk of concurrent infection. Quality metrics to be tracked prospectively based on time to initiation of treatment and clinical response were selected. CONCLUSION: HLH/MAS are increasingly considered to be a spectrum of related conditions, and joint management across subspecialties could improve patient outcomes. Our experience in creating a multidisciplinary approach to HLH/MAS management can serve as a model for care at other institutions.

Histopathologic Correlates of Familial Hemophagocytic Lymphohistiocytosis Isolated to the Central Nervous System.

Familial hemophagocytic lymphohistiocytosis (HLH) is an immune hyperactivation syndrome caused by mutations in genes associated with cytotoxic T-cell and NK-cell function. While neurological manifestations frequently accompany systemic inflammation at initial presentation, isolated central nervous system (CNS) involvement is rare, and the histological correlates are not well described. We present 3 patients (ages 5, 6, and 7 years) with CNS-isolated familial HLH, who presented with a variety of neurological symptoms and underwent brain biopsies for multifocal enhancing supratentorial and infratentorial lesions. Biopsy slides from all 3 patients revealed similar findings: perivascular lymphocytes, predominantly CD3+ T-cells (CD4>CD8) with occasional intramural infiltration of small vessels; scattered histiocytes without hemophagocytosis; parenchymal and leptomeningeal inflammation varying from mild and focal to severe and sheet-like with associated destructive lesions. There was no evidence of demyelination, neoplasia, or infection. Genetic testing identified compound heterozygous mutations in PRF1 (Patients 1 and 2) and UNC13D (Patient 3), with no evidence of systemic disease except decreased NK-cell function. All 3 patients were treated with hematopoietic stem cell transplantation with marked improvement of symptoms. These findings combined with the poor outcomes associated with delayed diagnosis and lack of aggressive treatment highlight the need to consider HLH in the differential diagnosis of inflammatory brain lesions.

Bone marrow engraftment and associated dermatologic sequelae in a three-yr-old after liver transplantation.

We present a case of a three-yr-old child with a history of multisystem Langerhans cell histiocytosis treated with systemic chemotherapy, who developed progressive liver failure and received an orthotopic split liver transplant while continuing on chemotherapy. One month following transplant, he developed acute graft-vs.-host disease of the skin and gastrointestinal tract. Peripheral blood chimerism studies post-transplant demonstrated an increasing predominance of donor lymphocytes and granulocytes. Shortly after, the patient developed vitiligo, and two yr after transplantation, the patient developed skin manifestations of psoriasis. We discuss and review the current literature, which demonstrates that chimerism following liver transplantation is rare and in our patient may be related to his profound immunosuppression around the time of liver transplant as well the development of acute graft-versus-host disease. While autoimmune disease can occur after solid organ and stem cell transplant, our patient developed skin manifestations of autoimmunity after liver transplantation, which is also rarely described.

BRAF V600E-Positive Multisite Langerhans Cell Histiocytosis in a Preterm Neonate.

Hemorrhagic pustules with a "blueberry muffin" appearance accompanied by respiratory failure in a neonate present a challenging differential diagnosis that includes infections and neoplasms. We present a case of multiorgan, multisite Langerhans cell histiocytosis (LCH), positive for the oncogenic BRAF V600E mutation, in a preterm neonate. Infants with LCH pose a diagnostic challenge due to their heterogeneous presentations. This case is unusual in that the newborn presented with severe multiorgan involvement. Due to the rare incidence, wide spectrum of clinical manifestations, and high mortality rate, clinicians must maintain a high index of suspicion for LCH.

Recent advances in the understanding of Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a proliferative disease of cells that share phenotypic characteristics with the primary antigen presenting cells of the epidermis. Its clinical manifestations are highly variable, extending from very benign forms to a disseminated, aggressive disease that causes significant mortality. Although many of the fundamental pathogenetic features of LCH have been enigmatic, recent advances have led to a much clearer understanding of the disease. In particular, careful molecular analyses of mouse models and human LCH samples suggest that LCH's cell of origin may not be the epidermal LC itself but a myeloid-derived precursor. Advanced genomic technologies have revealed the presence of activating, somatic BRAF mutations in the majority of patient specimens. Together, these observations have produced a new picture of LCH as a myeloid neoplasm. These advances are likely to have profound implications for the use of targeted therapeutics in LCH.

Neonatal enteroviral sepsis/meningoencephalitis and hemophagocytic lymphohistiocytosis: diagnostic challenges.

We present the clinical course of three neonates with proven enteroviral infection and an initial clinical picture suggestive of hemophagocytic lymphohistiocytosis (HLH). After a complete workup, only one was treated for HLH. Of particular interest, the first newborn presented with hemophagocytic cells in the cerebrospinal fluid (CSF) and proved to have enteroviral meningoencephalitis but was ultimately not diagnosed with HLH. A fourth infant, who fulfilled the diagnostic criteria for HLH but did not have enteroviral infection, is included for comparison. We suggest that severe neonatal enteroviral infection and HLH are difficult to distinguish. Careful assessment is recommended, as prognosis and treatment differ between these two entities. Literature regarding neonatal enteroviral infection and HLH is reviewed, to demonstrate the continuum between the inflammation triggered by enteroviral infection and the occurrence of HLH, as well as their comparable CSF findings.

Recurrent BRAF mutations in Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) has a broad spectrum of clinical behaviors; some cases are self-limited, whereas others involve multiple organs and cause significant mortality. Although Langerhans cells in LCH are clonal, their benign morphology and their lack (to date) of reported recurrent genomic abnormalities have suggested that LCH may not be a neoplasm. Here, using 2 orthogonal technologies for detecting cancer-associated mutations in formalin-fixed, paraffin-embedded material, we identified the oncogenic BRAF V600E mutation in 35 of 61 archived specimens (57%). TP53 and MET mutations were also observed in one sample each. BRAF V600E tended to appear in younger patients but was not associated with disease site or stage. Langerhans cells stained for phospho-mitogen-activated protein kinase kinase (phospho-MEK) and phospho-extracellular signal-regulated kinase (phospho-ERK) regardless of mutation status. High prevalence, recurrent BRAF mutations in LCH indicate that it is a neoplastic disease that may respond to RAF pathway inhibitors.

Langerhans cell histiocytosis: malignancy or inflammatory disorder doing a great job of imitating one?

Langerhans cell histiocytosis (LCH) is the unifying designation for a rare proliferative disorder that occurs predominantly in childhood and involves the main antigen-presenting cell of the epidermis. LCH can present in a multitude of ways, from a self-limited rash that resolves spontaneously to a systemic multi-organ disease with a 20% mortality rate. Because some forms behave in a relatively benign manner and are associated with an inflammatory cell infiltrate, it has been proposed that LCH might be a reactive disease. However, its neoplastic nature is suggested by the fact that the proliferating cells in LCH are clonal and overexpress p53. Nonetheless, no recurrent genomic, genetic or epigenetic abnormalities have been identified. Instead, a variety of molecular abnormalities that are consistent with disordered Langerhans cell maturation have been described. A faithful small animal model would aid our understanding of the pathophysiology of LCH but, to date, none exists. Challenges to the creation of a model include the lack of characteristically recurrent genetic abnormalities and the absence of a truly tissue-specific promoter to drive expression of genetic elements solely in Langerhans cells. Still, some of the phenotypic abnormalities in adhesion molecule or chemokine receptor expression might be modeled with sufficient precision to allow the testing of novel therapies.

Mutations of the hemophagocytic lymphohistiocytosis-associated gene UNC13D in a patient with systemic juvenile idiopathic arthritis.

The clinical syndromes of hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are both characterized by dysregulated inflammation with prolonged fever, hepatosplenomegaly, coagulopathy, hematologic cytopenias, and evidence of hemophagocytosis in the bone marrow or liver. While HLH is either inherited or acquired, children with severe rheumatic diseases, most notably systemic juvenile idiopathic arthritis, are at risk for MAS. The phenotypic similarity between HLH and MAS raises the possibility that they share common pathogenetic mechanisms. Familial forms of HLH have been attributed to mutations in the genes encoding perforin (PRF1) and Munc13-4 (UNC13D), among others, and are characterized by defective cytotoxic lymphocyte function. While some patients with systemic JIA have decreased levels of perforin protein expression and natural killer (NK) cell function, mutations of HLH-associated genes in patients with systemic JIA have not been reported. We report the case of an 8-year-old girl with systemic JIA without MAS who was found to have compound heterozygous mutations of UNC13D and reduced NK cell cytotoxic function. This case broadens the range of clinical phenotypes attributable to UNC13D mutations and offers new insights into the etiology and pathogenesis of systemic JIA.

Aggressive Langerhans cell histiocytosis following T-ALL: clonally related neoplasms with persistent expression of constitutively active NOTCH1.

Langerhans cell histiocytosis (LCH) and related entities are neoplasms of unknown pathogenesis. Here, we describe studies assessing the role of NOTCH1 mutations in LCH, which were based on a case of fatal Langerhans cell tumor after T-cell acute lymphoblastic leukemia (T-ALL). Although the two types of neoplasm in this patient were temporally and pathologically distinct, molecular analyses showed that they harbored the same T-cell receptor gene rearrangements and two activating NOTCH1 mutations involving exons 27 and 34. The exon 27 mutation altered a conserved cysteine residue in the N-terminal portion of the NOTCH1 heterodimerization domain, while the mutation in exon 34 introduced a premature stop codon that results in the deletion of C-terminal negative regulatory PEST domain. Analysis of cDNA prepared from the aggressive Langerhans cell tumor showed that the NOTCH1 mutations were aligned in cis, a configuration that caused synergistic increases in NOTCH1 signal strength in reporter gene assays. Immunohistochemistry confirmed that the Langerhans cell tumor also expressed NOTCH1 protein. Although these data suggested that NOTCH1 mutations might contribute to the pathogenesis of typical sporadic LCH and related neoplasms occurring in the absence of T-ALL, an analysis of 24 cases of LCH and Rosai-Dorfman Disease occurring in patients without an antecedent history of T-ALL revealed no mutations. Thus, activating NOTCH1 mutations appear to be unique to aggressive Langerhans cell tumors occurring after T-ALL. Persistent expression of NOTCH1 in such tumors suggests that Notch pathway inhibitors could have a role in the treatment of these unusual neoplasms.

Hematopoiesis following disruption of the Pitx2 homeodomain gene.

OBJECTIVE: Study the effect of loss of expression of Pitx2, a homeodomain gene preferentially expressed in murine hematopoietic stem/progenitor cells, on hematopoietic stem cells (HSCs). METHODS: We examined the fetal livers of mouse embryos with homozygous disruption of the Pitx2 gene, using flow cytometry immunophenotyping analysis, as well as immunohistochemistry techniques. We further investigated the role of Pitx2 in HSCs using a chimeric mouse model system. Pitx2 null embryonic stem (ES) cell clones were generated from embryonic day 3.5 blastocysts of Pitx2 null embryos. The Pitx2 null donor ES cell contribution to the adult hematopoietic system was confirmed by identifying donor-specific glucose-phosphate isomerase isotype in the erythrocytes using cellulose acetate eletrophoresis, and by demonstrating donor-specific major histocompatibility complex antigen allotype on the granulocytes/monocytes and T and B lymphocytes of the chimeric mice using flow cytometry analysis. RESULTS: Pitx2 homozygous null fetal livers are decreased in size and overall cellularity. The erythroid cell component of these livers is further reduced as compared to that of their wild-type and heterozygous littermates. Detailed quantitative analysis of the chimeric mice revealed contribution of Pitx2 null ES cells to erythroid, myeloid, lymphoid, and megakaryocytic lineages. The quantitative level of ES cell contribution to the peripheral hematopoietic cells was proportional to the level of general chimerism as determined by coat color. CONCLUSION: Although the fetal livers of Pitx2 null embryos displayed signs of impaired erythropoiesis, Pitx2 gene disrupted HSCs can contribute to hematopoiesis under physiological conditions.

Hemophagocytosis exacerbated by G-CSF/GM-CSF treatment in a patient with myelodysplasia.

We describe a 75-year-old man with neutropenia in whom bone marrow aspirate and biopsy demonstrated hemophagocytosis associated with myelodysplasia (MDS). Therapy with granulocyte-colony stimulating factor (G-CSF) and granulocyte-monocyte-colony stimulating factor (GM-CSF) caused splenomegaly and severe thrombocytopenia, which recurred upon rechallenge. We propose that myeloid growth factors may be detrimental in patients with MDS-associated hemophagocytosis.