Diagnostic yield of bone marrow aspiration in paediatric primary immune thrombocytopenia: impact of evolution and adherence to medical guidelines over the last 25 years

The aim of this study is to analyse the diagnostic value of bone marrow aspiration (BMA) in a retrospective cohort of patients with suspected immune thrombocytopaenia (ITP). We further measure changes in the percentage of patients who underwent this study and whether testing or not was in accordance with current guidelines at the time of diagnosis. We conducted a chart review of 243 patients with ITP who underwent follow-up in our institution between 1995 and 2022. The patients were divided into historical cohorts based on the practice guidelines of the Spanish Society of Pediatric Hematology and Oncology (SEHOP) and the American Society of Hematology (ASH) in place at the time of follow-up. For each case, time of disease presentation or initial diagnosis was defined as that which occurred in the first 72 h following disease onset. Based on data from the historical cohorts studied, we observed a lower total number of BMAs at diagnosis over time (p < 0.005). A gradual reduction was seen in the number of BMAs with the introduction of guidelines, including a progressively lower number of BMAs performed without indication (p < 0.05). Subsequent to the initial diagnosis, the procedure played a decisive role in only 2 patients (0.58%), allowing for a diagnosis of acquired aplastic anaemia in both cases. In both of them on diagnosis, BMA did not appear to be indicated, although subsequent analysis after 72 h raised suspicion of bone marrow failure.

CONCLUSION

BMA at presentation did not significantly alter the diagnosis in our cohort of patients with an initial suspicion of ITP, although the procedure was decisive in diagnosing 2 cases of acquired aplastic anaemia during the subsequent course of the disease. Regarding the number of aspirations performed, our findings show that increased physician compliance with current guidelines reduced the rate of unnecessary BMAs.

WHAT IS KNOWN

• BMA is a supplementary test for the diagnosis of ITP. • The usefulness of this invasive diagnostic procedure is not clearly stated in current guidelines.

WHAT IS NEW

• Adjustments to scientific guidelines have led to a reduction in the number of BMAs performed on our patients with suspected ITP in the last 27 years. • While the risks and benefits of BMA at the time of diagnosis are unclear in patients with suspected ITP, the procedure does not contribute significant information to support the diagnosis.

Haemoglobinopathies and other rare anemias in Spain: ten years of a nationwide registry (REHem-AR)

REHem-AR was created in 2013. The progressive implementation of neonatal screening for haemoglobinopathies in Spanish autonomous communities where the registry had not been implemented, as well as the addition of new centres during this period, has considerably increased the sample of patients covered. In this study, we update our previous publication in this area, after a follow-up of more than 5 years. An observational, descriptive, multicentre and ambispective study of adult and paediatric patients with haemoglobinopathies and rare anaemias registered in REHem was performed. The data are from a cross-sectional analysis performed on 1 June, 2023. The study population comprised 1,756 patients, of whom 1,317 had SCD, 214 had thalassaemia and 224 were diagnosed with another condition. Slightly more than one third of SCD patients (37%) were diagnosed based on neonatal bloodspot screening, and the mean age at diagnosis was 2.5 years; 71% of thalassaemia patients were diagnosed based on the presence of anaemia. Vaso-occlusive crisis and acute chest syndrome continue to be the most frequent complications in SCD. HSCT was performed in 83 patients with SCD and in 50 patients with thalassaemia. Since the previous publication, REHem-AR has grown in size by more than 500 cases. SCD and TM are less frequent in Spain than in other European countries, although the data show that rare anaemias are frequent within rare diseases. REHem-AR constitutes an important structure for following the natural history of rare anaemias and enables us to calculate investment needs for current and future treatments.

Optical Genome Mapping as a New Tool to Overcome Conventional Cytogenetics Limitations in Patients with Bone Marrow Failure

Cytogenetic studies are essential in the diagnosis and follow up of patients with bone marrow failure syndromes (BMFSs), but obtaining good quality results is often challenging due to hypocellularity. Optical Genome Mapping (OGM), a novel technology capable of detecting most types chromosomal structural variants (SVs) at high resolution, is being increasingly used in many settings, including hematologic malignancies. Herein, we compared conventional cytogenetic techniques to OGM in 20 patients with diverse BMFSs. Twenty metaphases for the karyotype were only obtained in three subjects (15%), and no SVs were found in any of the samples. One patient with culture failure showed a gain in chromosome 1q by fluorescence in situ hybridization, which was confirmed by OGM. In contrast, OGM provided good quality results in all subjects, and SVs were detected in 14 of them (70%), mostly corresponding to cryptic submicroscopic alterations not observed by standard techniques. Therefore, OGM emerges as a powerful tool that provides complete and evaluable results in hypocellular BMFSs, reducing multiple tests into a single assay and overcoming some of the main limitations of conventional techniques. Furthermore, in addition to confirming the abnormalities detected by conventional techniques, OGM found new alterations beyond their detection limits.

Madrid Newborn Sickle Cell Disease Cohort: clinical outcomes, stroke prevention and survival

In May 2003, Madrid established the universal newborn screening (NBS) for sickle cell disease (SCD). However, there are no studies resembling the evolution of a SCD neonate cohort followed according to national guidelines in Spain. The aim of this study is to describe the morbimortality and the stroke prevention programme in patients diagnosed by SCD NBS in Madrid. This is a multicentre, observational, prospective cohort study between 2003 and 2018; 187 patients diagnosed with SCD were included (151 HbSS, 6 HbSβ0, 27 HbSC, 3 HbSβ +), and median follow-up was 5.2 years (0.03-14.9). There were 5 deaths: 2 related to SCD in patients with severe genotype (HbSS/HbSβ0). Overall survival reached 95% and SCD-related survival 96.8%. The most frequent events were fever without focus, vaso-occlusive crises and acute chest syndromes. Eight strokes occurred in 5 patients which led to a 90.7% stroke-free survival in severe genotype patients (first stroke rate, 0.54 per 100 patient-years). Transcranial Doppler (TCD) was performed in 95% of eligible patients; 75% of children with pathological TCD remained stroke-free. Regarding HbSS/HbSβ0 patients, 50.1% received hydroxyurea and 9.5% haematopoietic stem cell transplantation. This study reflects the evolution of Madrid SCD cohort and provides morbimortality data similar to other developed countries.

Recommendations for the diagnosis and treatment of patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA) characterized by the development of microangiopathic haemolytic anaemia, thrombocytopenia, and ischaemic organ dysfunction associated with ADAMTS13 levels lower than 10% in most cases. Recently there have been numerous advances in the field of PTT, new, rapid and accessible techniques capable of quantifying ADAMTS13 activity and inhibitors. The massive sequencing systems facilitate the identification of polymorphisms in the ADAMTS13 gene. In addition, new drugs such as caplacizumab have appeared and relapse prevention strategies are being proposed with the use of rituximab. The existence of TTP patient registries allow a deeper understanding of this disease but the great variability in the diagnosis and treatment makes it necessary to elaborate guidelines that homogenize terminology and clinical practice. The recommendations set out in this document were prepared following the AGREE methodology. The research questions were formulated according to the PICO format. A search of the literature published during the last 10 years was carried out. The recommendations were established by consensus among the entire group, specifying the existing strengths and limitations according to the level of evidence obtained. In conclusion, this document contains recommendations on the management, diagnosis, and treatment of TTP with the ultimate objective of developing guidelines based on the evidence published to date that allow healthcare professionals to optimize TTP treatment.

T-Cell Depleted Haploidentical Transplantation in Children With Hematological Malignancies: A Comparison Between CD3+/CD19+ and TCRαβ+/CD19+ Depletion Platforms

Background

T-cell depleted (TCD) haploidentical transplantation using CD3+/CD19+ and TCRαβ+/CD19+ depletion techniques has been increasingly used in children with hematological malignancies. We present a retrospective study aimed to compare transplant outcomes in children with leukemia receiving a TCD haploidentical transplant using either CD3+/CD19+ or TCRαβ+/CD19+ platforms.

Methods

A total of 159 children with leukemia (ALL=80) (AML=79) that received a TCD haploidentical transplantation using either CD3+/CD19+ (n=79) or TCRαβ+/CD19+ (n=80) platforms between 2005 and 2020 were included. Median age was 9 years in both groups. There were no differences in patient, donor, and transplant characteristics between groups except for donor KIR B genotype more frequent in the TCRαβ+/CD19+ group (91%) than in the CD3+/CD19+ group (76%) (p=0.009) and a high number of NK+ cells and lower CD19+ cells infused in the TCRαβ+/CD19+ group (35.32x106/kg and 0.06 x106/Kg) than in the CD3+/CD19 group (24.6x106/Kg and 0.25 x106/Kg) (p=0.04 and p=0.0001), respectively. Conditioning was based on TBF. Median follow-up for survivors was 11 years (range; 8-16 y) in CD3+/CD19+ group and 5 years (range; 2-9 y) in the TCRαβ+/CD19+ group.

Results

Engraftment kinetics were similar in both groups (13 days for neutrophils and 10 days for platelets). There was no difference in the incidence of acute GvHD II-IV (29 ± 5% in the CD3+/CD19+ group vs 38 ± 5% in the TCRαβ+/CD19+ group) and chronic GvHD (32 ± 5% vs 23 ± 4%, respectively). NRM was 23 ± 5% in the CD3+/CD19+group vs 21 ± 4% in the TCRαβ+/CD19+group. Relapse incidence was also similar, 32 ± 5% vs 34 ± 6%, respectively. DFS and OS were not different (45 ± 5% vs 45 ± 6% and 53 ± 6% vs 58 ± 6% respectively). As there were no differences on transplant outcomes between groups, we further analyzed all patients together for risk factors associated with transplant outcomes. On multivariate analysis, we identified that early disease status at transplant (HR: 0.16; 95%CI (0.07-0.35) (p=0.0001), presence of cGvHD (HR: 0.38; 95%CI (0.20-0.70) (p= 0.002), and donor KIR-B genotype (HR: 0.50; 95%CI (0.32-0.90) (p=0.04) were associated with better DFS.

Conclusions

Our data suggest that there are no advantages in transplant outcomes between TCD platforms. Risk factors for survival are dependent on disease characteristic, donor KIR genotype, and chronic GvHD rather than the TCD platform used.

Mobilization with high-dose granulocyte colony-stimulating factor alone at 12 μg/kg twice a day in high-risk pediatric patients: A retrospective analysis of the experience in a single center

INTRODUCTION

Mobilization regimes in pediatric patients at high risk for poor mobilization are not standardized across different institutions. We present a retrospective analysis of our experience with a high-dose granulocyte colony-stimulating factor (G-CSF) regime of 12 μg/Kg per body weight (BW) twice a day for 4 days used in high-risk patients.

MATERIAL AND METHODS

We report the results of all pediatric patients mobilized with high-dose G-CSF between January 1999 and February 2021 in our center. A successful mobilization was defined as a peripheral blood (PB) CD34⁺ cell count of ≥10 CD34⁺ cells/μl on the fifth day of mobilization immediately before leukapheresis. A minimum cell yield of ≥2 × 10⁶ CD34⁺ cells/Kg of BW was required for a successful collection.

RESULTS

Of the 262 patients included in the analysis, mobilization failure was found in 27 (10.3%). In a univariate analysis, this was associated with age, weight, baseline diagnosis, and having undergone a previous mobilization cycle, the latter being the only factor that remained significantly associated in a multivariate analysis (P = 0.03). The 54 patients (20.6%) did not reach the minimum required CD34⁺ cell yield. 50.4% of the patients reported adverse events (AEs) during the mobilization period, and 23 (9.1%) reported 3 or more concomitant AEs. However, all of them were mild and did not affect the mobilization schedule.

CONCLUSIONS

Although most high-risk pediatric patients are successfully mobilized with the high-dose G-CSF regime, this approach does not salvage all of them and significantly increases the presence of AEs in comparison to standard-dose regimes.

Improved collection of hematopoietic stem cells and progenitors from Fanconi anemia patients for gene therapy purposes

Difficulties in the collection of hematopoietic stem and progenitor cells (HSPCs) from Fanconi anemia (FA) patients have limited the gene therapy in this disease. We have investigated (ClinicalTrials.gov, NCT02931071) the safety and efficacy of filgrastim and plerixafor for mobilization of HSPCs and collection by leukapheresis in FA patients. Nine of eleven enrolled patients mobilized beyond the threshold level of 5 CD34⁺ cells/μL required to initiate apheresis. A median of 21.8 CD34⁺ cells/μL was reached at the peak of mobilization. Significantly, the oldest patients (15 and 16 years old) were the only ones who did not reach that threshold. A median of 4.27 million CD34⁺ cells/kg was collected in 2 or 3 aphereses. These numbers were markedly decreased to 1.1 million CD34⁺ cells/kg after immunoselection, probably because of weak expression of the CD34 antigen. However, these numbers were sufficient to facilitate the engraftment of corrected HSPCs in non-conditioned patients. No procedure-associated serious adverse events were observed. Mobilization of CD34⁺ cells correlated with younger age, higher leukocyte counts and hemoglobin values, lower mean corpuscular volume, and higher proportion of CD34⁺ cells in bone marrow (BM). All these values offer crucial information for the enrollment of FA patients for gene therapy protocols.

Primary Immune Regulatory Disorders With an Autoimmune Lymphoproliferative Syndrome-Like Phenotype: Immunologic Evaluation, Early Diagnosis and Management

Primary immune regulatory disorders (PIRD) are associated with autoimmunity, autoinflammation and/or dysregulation of lymphocyte homeostasis. Autoimmune lymphoproliferative syndrome (ALPS) is a PIRD due to an apoptotic defect in Fas-FasL pathway and characterized by benign and chronic lymphoproliferation, autoimmunity and increased risk of lymphoma. Clinical manifestations and typical laboratory biomarkers of ALPS have also been found in patients with a gene defect out of the Fas-FasL pathway (ALPS-like disorders). Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA), we identified more than 600 patients suffering from 24 distinct genetic defects described in the literature with an autoimmune lymphoproliferative phenotype (ALPS-like syndromes) corresponding to phenocopies of primary immunodeficiency (PID) (NRAS, KRAS), susceptibility to EBV (MAGT1, PRKCD, XIAP, SH2D1A, RASGRP1, TNFRSF9), antibody deficiency (PIK3CD gain of function (GOF), PIK3R1 loss of function (LOF), CARD11 GOF), regulatory T-cells defects (CTLA4, LRBA, STAT3 GOF, IL2RA, IL2RB, DEF6), combined immunodeficiencies (ITK, STK4), defects in intrinsic and innate immunity and predisposition to infection (STAT1 GOF, IL12RB1) and autoimmunity/autoinflammation (ADA2, TNFAIP3,TPP2, TET2). CTLA4 and LRBA patients correspond around to 50% of total ALPS-like cases. However, only 100% of CTLA4, PRKCD, TET2 and NRAS/KRAS reported patients had an ALPS-like presentation, while the autoimmunity and lymphoproliferation combination resulted rare in other genetic defects. Recurrent infections, skin lesions, enteropathy and malignancy are the most common clinical manifestations. Some approaches available for the immunological study and identification of ALPS-like patients through flow cytometry and ALPS biomarkers are provided in this work. Protein expression assays for NKG2D, XIAP, SAP, CTLA4 and LRBA deficiencies and functional studies of AKT, STAT1 and STAT3 phosphorylation, are showed as useful tests. Patients suspected to suffer from one of these disorders require rapid and correct diagnosis allowing initiation of tailored specific therapeutic strategies and monitoring thereby improving the prognosis and their quality of life.

CRISPR-Cas9 Technology as a Tool to Target Gene Drivers in Cancer: Proof of Concept and New Opportunities to Treat Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a hematopoietic malignancy produced by a unique oncogenic event involving the constitutively active tyrosine-kinase (TK) BCR/ABL1. TK inhibitors (TKI) changed its prognosis and natural history. Unfortunately, ABL1 remains unaffected by TKIs. Leukemic stem cells (LSCs) remain, and resistant mutations arise during treatment. To address this problem, we have designed a therapeutic CRISPR-Cas9 deletion system targeting BCR/ABL1. The system was efficiently electroporated to cell lines, LSCs from a CML murine model, and LSCs from CML patients at diagnosis, generating a specific ABL1 null mutation at high efficiency and allowing the edited leukemic cells to be detected and tracked. The CRISPR-Cas9 deletion system triggered cell proliferation arrest and apoptosis in murine and human CML cell lines. Patient and murine-derived xenografts with CRISPR-edited LSCs in NOD SCID gamma niches revealed that normal multipotency and repopulation ability of CRISPR edited LSCs were fully restored. Normal hematopoiesis was restored, avoiding myeloid bias. To the best of our knowledge, we show for the first time how a CRISPR-Cas9 deletion system efficiently interrupts BCR/ABL1 oncogene in primary LSCs to bestow a therapeutic benefit. This study is a proof of concept for genome editing in all those diseases, like CML, sustained by a single oncogenic event, opening up new therapeutic opportunities.

Secondary immune thrombocytopenia in children: Characteristics and outcome of a large cohort from two Spanish centres

AIM

To evaluate the incidence and outcome of secondary immune thrombocytopenia (ITP) in a large cohort of paediatric Spanish patients.

METHODS

A retrospective observational study was conducted in two paediatric University hospitals in Spain between 2009 and 2019, which included children from 4 months to 18 years old diagnosed with ITP. Data were recorded from clinical charts: gender, age at diagnosis, coexisting condition and associated characteristics, outcome and treatment.

RESULTS

Secondary ITP was diagnosed in 87 out of 442 patients (19.6%). Post-immunisation ITP was seen in younger children. The onset of secondary ITP to autoimmune diseases (AD) and immunodeficiencies (ID) was at an older age and had more tendency to be insidious, and platelet level was higher than primary ITP. Mean time from ITP onset to AD diseases or ID diagnosis was 1.2 and 2.6 years, respectively. Whereas the cumulative incidence of remission was significantly higher in post-immunisation and post-viral infection (compared with primary ITP patients), it was worse in AD and ID patients.

CONCLUSIONS

Identification of secondary ITP is important as it predicts outcome. Most of them are diagnosed at ITP onset, but AD diseases and ID should be ruled out periodically as they are usually identified later.

[Autoimmune hemolytic anemia: Case review]

INTRODUCTION

Autoimmune hemolytic anemia (AIHA) is a rare and generally self-limiting disease in children.

MATERIAL AND METHODS

A descriptive cross-sectional study was performed in children under 18 years diagnosed with AIHA from January/1997 to July/2019. Clinical variables were collected and AIHA was classified according to the direct antiglobulin test (DAT) in warm AIHA (IgG+/-C3d) and cold AIHA (C3d). Response to treatment and evolution were analyzed.

RESULTS

25 patients were included and 72% were males. The median age at diagnosis was 2 years (range 0.4 to 9). Fever (72%), pallor (68%), jaundice (64%), hepatosplenomegaly and coluria (48%) were the most common presenting symptoms. The median hemoglobin at diagnosis was 5.4 g/dl. DAT was positive in 96%, with detection of IgG antibodies in 76%. A single case presented negative DAT. 20% of the patients associated another cytopenia, one of which was subsequently diagnosed with common variable immunodeficiency. Concomitant viral infection was suspected or documented in 32%. Most of the cases were self-limiting and responded to corticosteroid treatment (72%). Those with partial response (24%), mainly those associated with other cytopenias, required other lines of treatment (rituximab, mycophenolate, immunoglobulins). Complications (32%) and relapses (26%) were detected only in warm AIHA.

CONCLUSIONS

Our case series confirms that AIHA is a very rare disease in childhood. Most cases evolve favorably, although up to a quarter of them require second lines of treatment and, in exceptional cases, they need very aggressive treatments. These latter cases generally correspond to patients who present more than one cytopenia in the course of the disease.

Systemic lupus erythematosus presenting as thrombotic thrombocytopaenic purpura in a child: a diagnostic challenge

Thrombotic thrombocytopaenic purpura (TTP) is a life-threatening thrombotic microangiopathy characterised by microangiopathic haemolytic anaemia, thrombocytopaenia and organ ischaemia. TTP is caused by a severe functional deficiency of ADAMTS13 activity. We describe a 10-year-old girl presenting anaemia and thrombocytopaenia with schistocytes. Urine protein to creatinine ratio was within nephrotic range. ADAMTS13 activity was 0%, and no anti-ADAMTS13 antibodies were found. A renal biopsy showed deposits of IgG, C3 and C1q in the capillary membrane, compatible with class V lupus nephritis. Therapeutic plasma exchange (TPE) was performed in conjunction with therapy consisting of steroids and mycophenolate mofetil. After 11 months of follow-up, the patient remains in remission with normal ADAMTS13 activity. Although acquired TTP is a rare finding in children, differential diagnosis of thrombotic microangiopathy should include ADAMTS13 and the assay should be performed early. TTP treatment is based on TPE, although the underlying disease must be ruled out to optimise treatment and prevent relapse.

High-resolution copy number analysis of paired normal-tumor samples from diffuse large B cell lymphoma

Copy number analysis can be useful for assessing prognosis in diffuse large B cell lymphoma (DLBCL). We analyzed copy number data from tumor samples of 60 patients diagnosed with DLBCL de novo and their matched normal samples. We detected 63 recurrent copy number alterations (CNAs), including 33 gains, 30 losses, and nine recurrent acquired copy number neutral loss of heterozygosity (CNN-LOH). Interestingly, 20 % of cases acquired CNN-LOH of 6p21 locus, which involves the HLA region. In normal cells, there were no CNAs but we observed CNN-LOH involving some key lymphoma regions such as 6p21 and 9p24.1 (5 %) and 17p13.1 (2.5 %) in DLBCL patients. Furthermore, a model with some specific CNA was able to predict the subtype of DLBCL, 1p36.32 and 10q23.31 losses being restricted to germinal center B cell-like (GCB) DLBCL. In contrast, 8p23.3 losses and 11q24.3 gains were strongly associated with the non-GCB subtype. A poor prognosis was associated with biallelic inactivation of TP53 or 18p11.32 losses, while prognosis was better in cases carrying 11q24.3 gains. In summary, CNA abnormalities identify specific DLBCL groups, and we describe CNN-LOH in germline cells from DLBCL patients that are associated with genes that probably play a key role in DLBCL development.

Evaluating gene expression profiling by quantitative polymerase chain reaction to develop a clinically feasible test for outcome prediction in multiple myeloma

The gene expression profiles (GEPs) of 96 selected genes were analysed by real-time quantitative polymerase chain reaction (qPCR) with a TaqMan low-density array card in isolated tumour plasma cells (PCs) from 157 newly diagnosed multiple myeloma (MM) patients. This qPCR-based GEP correctly classified cases following the Translocation-cyclin D classification. Classic prognostic parameters and qPCR-based GEP predicted MM patient outcome and, although multivariate analyses revealed that cytogenetic risk (standard vs. high risk) was the variable that most strongly predicted prognosis, GEP added significant information for risk stratification. Considering only the standard risk cytogenetic patients, multivariate analyses revealed that high β2-microglobulin, low CDKN1A and high SLC19A1 gene expression levels independently predicted a short time-to-progression (TTP), while high International Staging System stage, low CDKN2B and high TBRG4 gene expression predicted poor overall survival (OS). A gene expression risk score enabled the division of standard risk patients into two groups with different TTPs (83% vs. 38% at 3 years, P < 0·0001) and OS rates (88% vs. 61% at 5 years; P = 0·003). This study demonstrates that quantitative PCR is a robust, accurate and feasible technique for implementing in the daily routine as a surrogate for GEP-arrays.

Molecular characterization of immunoglobulin gene rearrangements in diffuse large B-cell lymphoma: antigen-driven origin and IGHV4-34 as a particular subgroup of the non-GCB subtype

The pathogenesis of diffuse large B-cell lymphoma (DLBCL) remains partially unknown. The analysis of the B-cell receptor of the malignant cells could contribute to a better understanding of the DLBCL biology. We studied the molecular features of the immunoglobulin heavy chain (IGH) rearrangements in 165 patients diagnosed with DLBCL not otherwise specified. Clonal IGH rearrangements were amplified according to the BIOMED-2 protocol and PCR products were sequenced directly. We also analyzed the criteria for stereotyped patterns in all complete IGHV-IGHD-IGHJ (V-D-J) sequences. Complete V-D-J rearrangements were identified in 130 of 165 patients. Most cases (89%) were highly mutated, but 12 sequences were truly unmutated or minimally mutated. Three genes, IGHV4-34, IGHV3-23, and IGHV4-39, accounted for one third of the whole cohort, including an overrepresentation of IGHV4-34 (15.5% overall). Interestingly, all IGHV4-34 rearrangements and all unmutated sequences belonged to the nongerminal center B-cell-like (non-GCB) subtype. Overall, we found three cases following the current criteria for stereotyped heavy chain VH CDR3 sequences, two of them belonging to subsets previously described in CLL. IGHV gene repertoire is remarkably biased, implying an antigen-driven origin in DLBCL. The particular features in the sequence of the immunoglobulins suggest the existence of particular subgroups within the non-GCB subtype.

Kappa deleting element as an alternative molecular target for minimal residual disease assessment by real-time quantitative PCR in patients with multiple myeloma

BACKGROUND AND OBJECTIVES

Minimal residual disease (MRD) assessment by PCR in multiple myeloma (MM) has several shortcomings, including the lack of a suitable target. Kappa deleting element (KDE) rearrangements occur in virtually all Ig-lambda B-cell malignancies and in 1/3 of Ig-kappa are not affected by somatic hypermutation and, as in ALL, could be used as PCR targets.

METHODS

We have first investigated the incidence, gene segment usage, and CDR3 composition of IGK-KDE rearrangements in 96 untreated myeloma patients. Second, we tested 16 KDE gene rearrangements as molecular targets for MRD assessment by RQ-PCR using a germline reverse primer and a germline Taqman probe in combination with allele-specific oligonucleotides (ASO) as forward primers.

RESULTS

Monoclonal KDE rearrangements were amplified in 45% (43/96) of cases, monoallelic in 2/3 of them (29 cases), and biallellic in the remaining 14 cases. Overall, 88% of cases were successfully sequenced, KDE being equally frequently rearranged with VK and with intron-Recombination signal sequence (RSS). Median numbers of inserted and deleted nucleotides in the junctional region were one and five, respectively.

CONCLUSIONS

Using KDE rearrangements as additional PCR target for MRD assessment in MM improves the applicability of these studies in 9% of cases overall and in 20% of lambda cases. Its use in the latter subset could represent a significant advance.