T cell clonal expansion and STAT3 mutations: a characteristic feature of acquired chronic T cell-mediated pure red cell aplasia

Epidemiologic sequential analysis of pure red blood cell aplasia and T-cell large granular lymphocyte leukemia in Korea

Pure red cell aplasia (PRCA) is a rare hematologic syndrome characterized by anemia with marked reticulocytopenia and, in Asia, is often accompanied by T-cell large granular lymphocyte leukemia (T-LGL). Minimal research has been done on the epidemiology and sequential events of PRCA combined with T-LGL. This study identified 2801 PRCA and 840 T-LGL patients by using big data of the National Health Insurance Service between 2003 and 2022. The average annual crude incidence of PRCA was 2.77 per million and remained stable over 20 years, while T-LGL incidence was 0.82 per million with an increasing trend, possibly reflecting improved diagnostic accessibility. The average age for PRCA and T-LGL onset increased over the study period, consistent with aged society. Associated PRCA conditions are rheumatic diseases (10.5%), thymoma (4.7%), parvovirus infection (1.0%), inflammatory bowel diseases (0.8%), T-LGL (0.6%) and no specific cause (82.4%). Among 18 patients with both PRCA and T-LGL, PRCA preceded T-LGL (50%) or diagnosed concurrently (44%), suggesting that autoreactive T cells in PRCA which suppress erythropoiesis and sequentially evolve into clonal T cell proliferation and, eventually, T-LGL occurrence. This observation supports the hypothesis that both conditions might share a common pathogenic pathway. Further study should identify the causal relationship of PRCA diagnosis followed by T-LGL diagnosis.

Pure Red Cell Aplasia in a Patient with Thymic Hyperplasia, Hypogammaglobulinemia and Adult T-cell Leukemia/Lymphoma

Acquired pure red cell aplasia (PRCA), caused by thymic hyperplasia, is extremely rare. We herein report a previously healthy 41-year-old man who presented with severe anemia, lymphadenopathy, an upper mediastinal mass, and hypogammaglobulinemia. The patient was eventually diagnosed with PRCA and adult T-cell leukemia/lymphoma (ATLL). The mediastinal mass was pathologically diagnosed as thymic hyperplasia without clear ATLL invasion. Although his anemia improved rapidly after thymectomy, PRCA recurred approximately 500 days later and was accompanied by ATLL exacerbation. The findings in this patient suggest that the Good's syndrome-like symptoms (thymic hyperplasia and hypogammaglobulinemia) in this patient and PRCA may have been paraneoplastic syndromes caused by ATLL.

Clinical features and outcomes in large granular lymphocyte leukemia - associated pure red cell aplasia with STAT3 mutation

Large granular lymphocyte leukemia (LGLL) is a rare lymphoproliferative disorder where somatic STAT3 mutation is common. Although LGLL has been described as an underlying condition associated with pure red cell aplasia (PRCA), the clinical characteristics and therapeutic response of LGLL - associated PRCA are largely unclear. We evaluated a set of 81 patients with LGLL - associated PRCA. Comparative analysis was performed on the clinical characteristics, responses to immunosuppressive therapy, and survival outcomes in patients with STAT3 mutation. Among the 81 LGLL - associated PRCA patients, 21 cases (26%) were STAT3 mutant, and 60 were wild - type. Of 21 patients with STAT3 mutation, 15 cases (71%) were positive for exon 21 mutation, 4 cases (19%) for exon 20 mutation, one for dual mutation in exon 20 and 21, and one for exon 13 mutation. The Y640F was the most commonly detected mutation (42.9%). Patients with STAT3 mutations had a higher percentage of reticulocytes (0.88% vs. 0.28%, P = 0.039) and red cell distribution width - coefficient of variation (18.8% vs. 15.8%, P = 0.008) compared to wild - type. Those with the STAT3 Y640F mutation had a younger median age at onset (44 years vs. 65 years, P = 0.007) and a higher peripheral blood lymphocyte ratio (63.7% vs. 34.4%, P = 0.033). The complete response rate (CRR) and overall response rate (ORR) of STAT3 mutated patients treated with cyclosporine (CsA) were 31.3% (5/16) and 56.3% (9/16), respectively, with no difference compared to the STAT3 wild - type (32.8%, 50%) (P = 0.909; P = 0.658). Although no statistical significance was found, the CRR and ORR of the CP regimen (consisted of cyclophosphamide and prednisone) were higher than CsA among STAT3 mutated individuals (53.8% vs. 31.3%, P = 0.274; 84.6% vs. 56.3%, P = 0.130). Reduction or discontinuation of immunosuppressive agents was the main cause of relapse. The relapse rate of the CP regimen was lower than CsA in this whole cohort (24.0% vs. 68.4%, P = 0.001), as well as in the STAT3 mutant group (18.2% vs. 77.8%, P = 0.022). STAT3 Y640F was the most common hotspot mutation in LGLL - associated PRCA. Patients with STAT3 mutation treated with CsA showed comparable responses to wild - type. CP regimen had a lower relapse rate and could be considered as a salvage therapy after CsA failure.

Efficacy and influencing factors of immunosuppressive therapy for pure red cell aplasia: meta-analysis and systematic review

Acquired pure red cell aplasia (aPRCA) is a rare hematological syndrome characterized by anemia and a significant reduction in erythroid progenitor cells. Immunosuppressive therapy (IST), including Corticosteroids (CS), Cyclosporine (CsA), and cyclophosphamide (CYC), is the primary treatment. However, variations in clinical efficacy and limited comparative studies have created uncertainty in therapeutic choices. This study aims to evaluate the efficacy of IST and the factors influencing treatment outcomes. A systematic search was conducted using PubMed, Embase, Cochrane Library, and Web of Science. Two researchers independently screened studies and extracted data. The quality of studies was assessed using the MINORS scale. Meta-analysis was performed using STATA/MP16, and effect size (ES) was calculated using fixed- or random-effects models based on heterogeneity. A total of 33 studies involving 1,193 patients were included. The overall efficacy of IST was significant, with a pooled ES of 0.656 (95% CI: 0.600-0.710). CsA demonstrated the highest efficacy (ES = 0.699; 95% CI: 0.615-0.779), followed by CYC (ES = 0.592; 95% CI: 0.423-0.752) and CS (ES = 0.568; 95% CI: 0.457-0.676). Subgroup analyses revealed that factors such as etiology, combination therapies, first- vs. second-line treatment, and genetic characteristics significantly influenced outcomes. Notably, the response to IST was higher in primary aPRCA (ES = 0.667; 95% CI: 0.598-0.733) compared to LGLL-associated (ES = 0.515; 95% CI: 0.393-0.637) and thymoma-associated (ES = 0.690; 95% CI: 0.492-0.864) aPRCA. The combination of CS and CsA yielded superior efficacy (ES = 0.761; 95% CI: 0.658-0.853) compared to combination of CS and CsA and monotherapy. First-line treatment demonstrated better efficacy than second-line treatment (ES = 0.659; 95% CI: 0.596-0.720) vs. (ES = 0.452; 95% CI: 0.199-0.715). The important finding was that (ES = 0.861; 95% CI: 0.595-1.000) in the STAT3 mutation (+) group and (ES = 0.375; 95% CI: 0.034-0.801) in the STAT3 mutation (-) group. IST demonstrates overall efficacy in aPRCA, with variations influenced by etiology, drug combinations, and genetic mutations such as STAT3. These findings highlight the need for personalized treatment strategies and further research to validate and optimize IST efficacy.

Mutational heterogeneities in STAT3 and clonal hematopoiesis-related genes in acquired pure red cell aplasia

Dysregulation of T cell-mediated immunity is considered a major pathophysiological mechanism in acquired pure red cell aplasia (PRCA), including idiopathic PRCA, large granular lymphocytic leukemia-associated PRCA, and thymoma-associated PRCA. Although STAT3 mutations are frequently detected in PRCA patients, the roles of other mutational profiles and their impact on clinical characteristics remain unclear. In this study, whole-exome sequencing and targeted sequencing using a custom-designed panel were performed on 53 PRCA patients. The most frequently mutated genes were STAT3 (36%), PCLO (9%), TET2 (9%), NEB (6%), DNMT3A (6%), and POT1 (6%). Based on genetic profiles, patients were classified into three groups: those with STAT3 variants (group S), those without STAT3 variants but with variants in clonal hematopoiesis (CH)-related genes (group C), and those without variants in either STAT3 or CH-related genes (group O). Patients in group O had a higher median age compared to group S, while group S exhibited milder anemia severity than group C. Additionally, POT1 variants were associated with the idiopathic subtype of PRCA in females, often co-occurring with STAT3 variants. Variants in CH-related genes and other genes, including STAT3 and POT1, may play crucial roles in the pathophysiology of PRCA.

A CML Patient Carrying BCR::ABL1 Splicing Variants Did Not Experience Blast Crisis for 15 Years without Responding to Various TKIs

A 45-year-old man was diagnosed with CML in the chronic phase and therefore was sequentially treated with imatinib, dasatinib, nilotinib, and ponatinib. Neither ABL1 point mutations nor any additional chromosomal abnormalities were detected. The patient's best response was a partial cytogenetic response to nilotinib treatment. The deletion of amino acid residues 184-274 and a 35 bp insertion after nucleotide 1423 of ABL1 were detected before ponatinib administration. Two years after ponatinib administration, the patient died of a traumatic brain hemorrhage 15 years after the CML diagnosis. He did not progress to blast crisis, possibly because of the emergence of a loss-of-function ABL1 splicing variant.

T-cell Large Granular Lymphocytic Leukemia with a STAT3 Mutation Successfully Treated with Cord Blood Transplantation

A 64-year-old woman presented with agranulocytosis, anemia, and bacteremia, leading to a diagnosis of T-cell large granular lymphocytic leukemia (T-LGLL). A molecular analysis identified a signal transducer and activator of transcription 3 (STAT3) Y640F variant. Initial treatment with cyclophosphamide and prednisolone did not improve her condition, but serious infections were observed. The patient underwent cord blood transplantation (CBT) after preconditioning with fludarabine, busulfan, and total body irradiation, yielding a STAT3 Y640F variant disappearance, based on allele-specific quantitative polymerase chain reaction (AS-qPCR). In this case, CBT is a promising refractory T-LGLL treatment option, and the STAT3 Y640F variant AS-qPCR is a T-LGLL activity marker.

Umbilical Cord Blood and UC-MSCs Combined with Low-Dose Immunosuppressant in the Treatment of Elderly Patients with Pure Red Cell Aplastic: A Case Series

INTRODUCTION

At present, cyclosporine (CsA) is the first-line treatment for Pure Red Cell Aplasia (PRCA), but CsA administration can be associated with a number of side effects due to its high toxicity. Therefore, it is urgent to explore a safe and effective treatment for elderly patients who cannot be treated with conventional doses of CsA, especially those with multiple complications. Allogeneic Stem Cell Transplantation (ASCT) for PRCA is a promising treatment, but reports of using umbilical cord blood (UCB) are very rare.

CASE PRESENTATION

In this report, UCB and umbilical cord mesenchymal stem cells (UC-MSCs) combined with low-dose CsA (1-3mg/kg/d) were used to treat 3 elderly patients who were diagnosed with PRCA combined with multiple complications in heart, lung, and renal. The treatments were successful without complications, and 12 months after stem cell infusion, the blood tests of the patients came normal. Moreover, the function of the liver, heart, and kidney continued to be stable.

CONCLUSION

This report provides an effective regimen of using UCB and UC-MSCs combined with low-dose CsA (1-3 mg/kg/d) to treat PRCA, especially for elderly patients with multiple complications who cannot use the conventional dosage.

Lenalidomide-induced pure red cell aplasia is associated with elevated expression of MHC-I molecules on erythrocytes

The RVd therapy, combining lenalidomide, bortezomib, and dexamethasone, is a mainstay treatment for multiple myeloma. A multiple myeloma patient developed pure red cell aplasia (PRCA) following RVd treatment, despite the absence of common PRCA triggers. In vitro analyses reveal lenalidomide as a pivotal disruptor of erythropoiesis. Single-cell transcriptome analysis unveils hyperactive CD8+ T cells and impaired erythropoiesis in the patient's bone marrow. Unexpectedly, the patient's erythroid cells display abnormally high expression of genes in the antigen presentation pathway, particularly those for major histocompatibility class I (MHC-I) molecules. Functional assays demonstrate that lenalidomide treatment further augmented MHC-I expression in the patient's erythroid cells. Blocking MHC-I or depleting T cells alleviates the defective erythropoiesis of PRCA, suggesting that the interaction between erythroid cells with elevated MHC-I and T cells in the bone marrow might contribute to PRCA. Taken together, our study implicates a mechanism underlying lenalidomide-induced PRCA in treating cancer patients.

The constitutive activation of STAT3 gene and its mutations are at the crossroad between LGL leukemia and autoimmune disorders

Type T Large Granular Lymphocyte Leukemia (T-LGLL) is a chronic disorder characterized by the abnormal proliferation of clonal cytotoxic T cells. The intriguing association of T-LGLL with autoimmune and inflammatory diseases, the most prominent example being rheumatoid arthritis, raises questions about the underlying pathophysiologic relationships between these disorders which share several biological and clinical features, most notably neutropenia, which is considered as a clinical hallmark. Recent progress in molecular genetics has contributed to a better understanding of pathogenetic mechanisms, thus moving our knowledge in the field of LGL leukemias forward. Focusing on the constitutive activation of STAT3 pathway and the well-established role of STAT3 mutations in T-LGLL, we herein discuss whether the T cell clones occurring in comorbid conditions are the cause or the consequence of the immune-inflammatory associated events. Overall, this review sheds light on the intricate relationships between inflammation and cancer, emphasizing the importance of the STAT3 gene and its activation in the pathophysiology of these conditions. Gaining a deeper understanding of these underlying mechanisms seeks to pave the way for the development of novel targeted therapies for patients affected by inflammation-related cancers.

Treatment strategy for acquired pure red cell aplasia: a systematic review and meta-analysis

The treatment of autoimmune acquired pure red cell aplasia (aPRCA) is challenging. Guidelines are based on expert recommendations in the absence of controlled trials. We assessed the efficacy of the main treatment strategy through a systematic review and meta-analysis using MEDLINE, EMBASE, and the Cochrane Library up to September 2022. The overall response rate (ORR) was pooled using random-effects models. In total, 24 observational studies (19 retrospective, median follow-up of 48 months) encompassing 753 patients (49% male) were included. Primary aPRCA represented 57% of the cases. The risk of bias was moderate to high using the ROBINS-I tool. Substantial heterogeneity (I2 > 50%) was retrieved. Corticosteroids as monotherapy as first-line treatment (186 patients, 13 studies) provided an ORR of 47% (95% confidence interval [CI], 34-60). Cyclosporine A was the most frequently used immunosuppressant agent (384 patients, 18 studies), providing an ORR of 74% (95% CI, 66-82) with a similar ORR in first- (73%) and second-line (76%) treatment and when cyclosporin was used as monotherapy (83%) or with corticosteroids (77%). A total of 112 patients (10 studies) received cyclophosphamide, with an ORR of 49% (95% CI, 35-64), which was higher when cyclophosphamide was combined with corticosteroids (48%) and used in second-line treatment (58%) than in monotherapy (31%), and in first-line treatment (44%). Sirolimus use was reported only after cyclosporine A failure and provided an ORR of 87% (95% CI, 68-100; 64 patients, 3 studies). Substantial uncertainty remains regarding the best treatment strategy in the absence of high-quality evidence. This study was registered on the PROPERO database as #CRD42022360452.

Pure red cell aplasia: The second hundred years

Pure red cell aplasia (PRCA) is a rare hematologic syndrome, characterized by an isolated normocytic anemia with severe reticulocytopenia, and defined by absence or near absence of erythroid precursors in the bone marrow. First described in 1922, PRCA may be a primary autoimmune or clonal myeloid or lymphoid disorder, but may also be secondary to other disorders of immune dysregulation/autoimmunity, to infections, to neoplasms, or to drugs. Insights from the study of PRCA have helped illuminate the understanding of the regulation of erythropoiesis. This review summarizes the classification, diagnostic, and therapeutic approach to PRCA as it begins its second century, with a particular focus on opportunities and challenges provided by new developments in the role of T-cells and T-cell regulatory mutations; the role of clonal hematopoiesis; and new developments in therapy for refractory PRCA and PRCA associated with ABO incompatible stem cell transplantation.

Not all LGL leukemias are created equal

Large Granular Lymphocyte (LGL) Leukemia is a rare, heterogeneous even more that once thought, chronic lymphoproliferative disorder characterized by the clonal expansion of T- or NK-LGLs that requires appropriate immunophenotypic and molecular characterization. As in many other hematological conditions, genomic features are taking research efforts one step further and are also becoming instrumental in refining discrete subsets of LGL disorders. In particular, STAT3 and STAT5B mutations may be harbored in leukemic cells and their presence has been linked to diagnosis of LGL disorders. On clinical grounds, a correlation has been established in CD8+ T-LGLL patients between STAT3 mutations and clinical features, in particular neutropenia that favors the onset of severe infections. Revisiting biological aspects, clinical features as well as current and predictable emerging treatments of these disorders, we will herein discuss why appropriate dissection of different disease variants is needed to better manage patients with LGL disorders.

Distinct mutational pattern of T-cell large granular lymphocyte leukemia combined with pure red cell aplasia: low mutational burden of STAT3

T-cell large granular lymphocyte leukemia (T-LGL) is often accompanied by pure red cell aplasia (PRCA). A high depth of next generation sequencing (NGS) was used for detection of the mutational profiles in T-LGL alone (n = 25) and T-LGL combined with PRCA (n = 16). Beside STAT3 mutation (41.5%), the frequently mutated genes included KMT2D (17.1%), TERT (12.2%), SUZ12 (9.8%), BCOR (7.3%), DNMT3A (7.3%), and RUNX1 (7.3%). Mutations of the TERT promoter showed a good response to treatment. 3 of 41 (7.3%) T-LGL patients with diverse gene mutations were revealed as T-LGL combined with myelodysplastic syndrome (MDS) after review of bone marrow slide. T-LGL combined with PRCA showed unique features (low VAF level of STAT3 mutation, low lymphocyte count, old age). Low ANC was detected in a STAT3 mutant with a low level of VAF, suggesting that even the low mutational burden of STAT3 is sufficient for reduction of ANC. In retrospective analysis of 591 patients without T-LGL, one MDS patient with STAT3 mutation was revealed to have subclinical T-LGL. T-LGL combined with PRCA may be classified as unique subtype of T-LGL. High depth NGS can enable sensitive detection of concomitant MDS in T-LGL. Mutation of the TERT promoter may indicate good response to treatment of T-LGL, thus, its addition to an NGS panel may be recommended.

Large granular lymphocyte leukemia: An indolent clonal proliferative disease associated with an array of various immunologic disorders

Large granular lymphocyte leukemia (LGLL) is a chronic lymphoproliferative disorder characterized by the proliferation of T or NK cytotoxic cells in the peripheral blood, the spleen and the bone marrow. Neutropenia leading to recurrent infections represents the main manifestation of LGLL. One specificity of LGLL is its frequent association with auto-immune disorders, among them first and foremost rheumatoid arthritis, and other hematologic diseases, including pure red cell aplasia and bone marrow failure. The large spectrum of manifestations and the classical indolent course contribute to the diagnosis difficulties and the frequency of underdiagnosed cases. Of importance, the dysimmune manifestations disappear with the treatment of LGLL as the blood cell counts normalize, giving a strong argument for a pathological link between the two entities. The therapeutic challenge results from the high rate of relapses following the first line of immunosuppressive drugs. New targeted agents, some of which are currently approved in autoimmune diseases, appear to be relevant therapeutic strategies to treat LGLL, by targeting key activated pathways involved in the pathogenesis of the disease, including JAK-STAT signaling.

All that glitters is not LGL Leukemia

LGL disorders are rare hematological neoplasias with remarkable phenotypic, genotypic and clinical heterogeneity. Despite these constraints, many achievements have been recently accomplished in understanding the aberrant pathways involved in the LGL leukemogenesis. In particular, compelling evidence implicates STAT signaling as a crucial player of the abnormal cell survival. As interest increases in mapping hematological malignancies by molecular genetics, the relevance of STAT gene mutations in LGL disorders has emerged thanks to their association with discrete clinical features. STAT3 and STAT5b mutations are recognized as the most common gain-of-function genetic lesions up to now identified in T-LGL leukemia (T-LGLL) and are actually regarded as the hallmark of this disorder, also contributing to further refine its subclassification. However, from a clinical perspective, the relationships between T-LGLL and other borderline and overlapping conditions, including reactive cell expansions, clonal hematopoiesis of indeterminate potential (CHIP) and unrelated clonopathies are not fully established, sometimes making the diagnosis of T cell malignancy challenging. In this review specifically focused on the topic of clonality of T-LGL disorders we will discuss the rationale of the appropriate steps to aid in distinguishing LGLL from its mimics, also attempting to provide new clues to stimulate further investigations designed to move this field forward.

Gain-of-function defects in toll-like receptor 8 shed light on the interface between immune system and bone marrow failure disorders

In this article, we will share lessons that patients with gain-of-function defects in Toll-like receptor 8 (TLR8-GOF) can teach us about the interface between bone marrow failure (BMF) disorders and inborn errors of immunity (IEI), subsequently referred to as “Interface Disorders”. TLR8-GOF is a relatively young entity (from a discovery standpoint) that—through both similar and dissimilar disease characteristics—can increase our understanding of interface disorders, for example, as it pertains to pathophysiology, the genetic mechanism of disease, and related diagnostics and therapeutics. From a genetics point of view, TLR8-GOF joins a growing list of (interface) disorders that can cause disease both with germline and somatic (mosaic) genetic variants. This not only has repercussions for the diagnostic workup of these disorders, inasmuch that routine genetic testing may miss somatic variants, but has therapeutic implications as well, for example, with the approach to curative treatment, such as hematopoietic stem cell transplantation. Following an introduction and schematic rendering of the interface, we will review the salient features of TLR8-GOF, with the understanding that the phenotype of this new disorder is likely not written in stone yet. In keeping with the principle of “Form Follows Function”, we will discuss specific immunological biomarkers that can be measured in clinical laboratories and highlight key disease features that pertain to TLR8-GOF, and can be found in several interface disorders. As can be seen from a schematic representation, the interface provides not only opportunities for learning and collaboration with respect to shared diagnostics but also the potential for drug repurposing and precision therapeutics. Ideally, collaboration also focuses on education and teaching, such that cross-fertilization and collaboration across these disciplines can create a framework for complementary research.