Spanish registry of hemoglobinopathies and rare anemias (REHem-AR): demographics, complications, and management of patients with ß-thalassemia.

INTRODUCTION: The increase in the number of patients with hemoglobinopathies in Europe in recent decades highlights the need for more detailed epidemiological information in Spain. To fulfil this need, the Spanish Society of Pediatric Hematology and Oncology (SEHOP) sponsored the creation of a national registry of hemoglobinopathies known as REHem-AR (Spanish Registry of Hemoglobinopathies and Rare Anemias). Data from the transfusion-dependent (TDT) and non-transfusion-dependent (NTDT) ß-thalassemia cohorts are described and analyzed. METHODS: We performed an observational, multicenter, and ambispective study, which included patients of any age with TDT and NTDT, registered up to December 31, 2021. RESULTS: Among the 1741 patients included, 168 cases of thalassemia were identified (103 TDT and 65 NTDT-patients). Survival at 18 years was 93% for TDT and 100% for NTDT. Regarding management, 80 patients with TDT (77.7%) and 23 patients with NTDT (35.4%) started chelation treatment during follow-up, with deferasirox being the most widely used. A total of 76 patients within the TDT cohort presented at least 1 complication (73.8%), the most frequent being hemosiderosis and osteopenia-osteoporosis. Comparison of both cohorts revealed significant differences in the diagnosis of hepatic hemosiderosis (p = 0.00024), although these were not observed in the case of cardiac iron overload (p = 0.27). DISCUSSION: Our registry enabled us to describe the management of ß thalassemia in Spain and to analyze the morbidity and mortality of the cohorts of patients with TDT and NTDT. Complications related to iron overload in TDT and NTDT account for most of the morbidity and mortality of the disease, which is associated with a considerable social, psychological, and economic impact, although cardiac, osteopathy and endocrinological complications requiring more attention. The convenience and simplicity of online registries make it possible to homogenize variables and periodically update data, thus providing valuable information on these diseases.

Tapering of the thrombopoietin receptor agonist in paediatric patients with chronic immune thrombocytopenia: Is it possible?

It is not clear if platelet responses are sustained after thrombopoietin receptor agonist (ar-TPO) withdrawal in paediatric patients. A multicentre retrospective observational study was performed in children with chronic immune thrombopenia (cITP) to describe ar-TPO tapering and withdrawal in patients who had achieved a sustained complete response to ar-TPOs. Ten patients (eltrombopag n = 6, romiplostim n = 4) were included. Treatment withdrawal was performed after a mean tapering time of 7.6 months. Two patients relapsed (median follow-up time of 24 months). Slow tapering and withdrawal of ar-TPOs can be safely performed in cITP paediatric patients after achieving a sustained complete response.

Natural gene therapy by reverse mosaicism leads to improved hematology in Fanconi anemia patients.

Fanconi anemia (FA) is characterized by chromosome fragility, bone marrow failure (BMF) and predisposition to cancer. As reverse genetic mosaicism has been described as "natural gene therapy" in patients with FA, we sought to evaluate the clinical course of a cohort of FA mosaic patients followed at referral centers in Spain over a 30-year period. This cohort includes patients with a majority of T cells without chromosomal aberrations in the DEB-chromosomal breakage test. Relative to non-mosaic FA patients, we observed a higher proportion of adult patients in the cohort of mosaics, with a later age of hematologic onset and a milder evolution of (BMF). Consequently, the requirement for hematopoietic stem cell transplant (HSCT) was also lower. Additional studies allowed us to identify a sub-cohort of mosaic FA patients in whom the reversion was present in bone marrow (BM) progenitor cells leading to multilineage mosaicism. These multilineage mosaic patients are older, have a lower percentage of aberrant cells, have more stable hematology and none of them developed leukemia or myelodysplastic syndrome when compared to non-mosaics. In conclusion, our data indicate that reverse mosaicism is a good prognostic factor in FA and is associated with more favorable long-term clinical outcomes.

Optimised molecular genetic diagnostics of Fanconi anaemia by whole exome sequencing and functional studies.

PURPOSE: Patients with Fanconi anaemia (FA), a rare DNA repair genetic disease, exhibit chromosome fragility, bone marrow failure, malformations and cancer susceptibility. FA molecular diagnosis is challenging since FA is caused by point mutations and large deletions in 22 genes following three heritability patterns. To optimise FA patients' characterisation, we developed a simplified but effective methodology based on whole exome sequencing (WES) and functional studies. METHODS: 68 patients with FA were analysed by commercial WES services. Copy number variations were evaluated by sequencing data analysis with RStudio. To test FANCA missense variants, wt FANCA cDNA was cloned and variants were introduced by site-directed mutagenesis. Vectors were then tested for their ability to complement DNA repair defects of a FANCA-KO human cell line generated by TALEN technologies. RESULTS: We identified 93.3% of mutated alleles including large deletions. We determined the pathogenicity of three FANCA missense variants and demonstrated that two FANCA variants reported in mutations databases as 'affecting functions' are SNPs. Deep analysis of sequencing data revealed patients' true mutations, highlighting the importance of functional analysis. In one patient, no pathogenic variant could be identified in any of the 22 known FA genes, and in seven patients, only one deleterious variant could be identified (three patients each with FANCA and FANCD2 and one patient with FANCE mutations) CONCLUSION: WES and proper bioinformatics analysis are sufficient to effectively characterise patients with FA regardless of the rarity of their complementation group, type of mutations, mosaic condition and DNA source.

[Reduced-intensity conditioning haematopoietic stem cell transplantation in genetic diseases: Experience of the Spanish Working Group for Bone Marrow Transplantation in Children]. / Trasplante de progenitores hematopoyéticos con intensidad reducida en enfermedades genéticas. Experiencia del grupo GETMON (Grupo Español de Trasplante de Médula Ósea en Niños).

INTRODUCTION: Haematopoietic stem cell transplantation (HSCT) involves implanting cellular elements capable of generating a new and healthy haematopoietic system. Reduced intensity conditioning (RIC) consists of an immunosuppressive treatment to facilitate a progressive implant with lower morbidity. This type of conditioning can also lead to myelosuppression, which is potentially reversible over time. Reduced intensity conditioning enables HSCT to be performed on patients with genetic diseases for whom added comorbidity is undesirable due to the high doses of chemotherapy that accompanies conventional myeloablative regimens. PATIENTS AND METHODS: An analysis was performed on the outcomes of 68 paediatric patients with genetic diseases who underwent HSCT with RIC between 2005 and 2013 in the of Paediatric Haematopoietic Stem Cell Transplantation Units that are part of the Spanish Working Group for Bone Marrow Transplantation in Children. A multicentre study was conducted including 68 patients, of whom 43 had Primary Immunodeficiency, 21 with congenital haematological diseases, and 4 with metabolic diseases. RESULTS: Fifty (73.5%) of the 68 patients were still alive. The Overall Survival (OS) at nine years was 0.74. Twenty-three (33.8%) had some event during the course of the HSCT, with an event-free survival rate of 0.66. The OS in patients with haematological diseases was 0.81, being 0.7 in primary immunodeficiencies, and 0.4 in metabolic diseases. No significant difference was observed between the 3 groups of diseases. As regards the source of haematopoietic progenitors, there was an OS rate of 0.74 in patients transplanted with peripheral blood, 0.70 with bone marrow, and 0.70 and with cord blood, with no statistically significant differences. CONCLUSIONS: Favourable results have been obtained in HSCT with reduced intensity conditioning in genetic diseases. It should be noted that the risks and benefits of the RIC in patients with metabolic diseases need to be assessed on an individual basis.

National registry of hemoglobinopathies in Spain (REPHem).

BACKGROUND: Although highly prevalent throughout the world, the accurate prevalence of hemoglobinopathies in Spain is unknown. PROCEDURE: This study presents data on the national registry of hemoglobinopathies of patients with thalassemia major (TM), thalassemia intermedia (TI), and sickle cell disease (SCD) in Spain created in 2014. Fifty centers reported cases retrospectively. Data were registered from neonatal screening or from the first contact at diagnosis until last follow-up or death. RESULTS: Data of the 715 eligible patients were collected: 615 SCD (497 SS, 64 SC, 54 SBeta phenotypes), 73 thalassemia, 9 CC phenotype, and 18 other variants. Most of the SCD patients were born in Spain (65%), and 51% of these were diagnosed at newborn screening. Median age at the first diagnosis was 0.4 years for thalassemia and 1.0 years for SCD. The estimated incidence was 0.002 thalassemia cases and 0.03 SCD cases/1,000 live births. Median age was 8.9 years (0.2-33.7) for thalassemia and 8.1 years (0.2-32.8) for SCD patients. Stroke was registered in 16 SCD cases. Transplantation was performed in 43 TM and 23 SCD patients at a median age of 5.2 and 7.8 years, respectively. Twenty-one patients died (3 TM, 17 SCD, 1 CC) and 200 were lost to follow-up. Causes of death were related to transplantation in three patients with TM and three patients with SCD. Death did not seem to be associated with SCD in six patients, but nine patients died secondary to disease complications. Overall survival was 95% at 15 years of age. CONCLUSIONS: The registry provides data about the prevalence of hemoglobinopathies in Spain and will permit future cohort studies and the possibility of comparison with other registries.

Functional and clinical impact of novel TMPRSS6 variants in iron-refractory iron-deficiency anemia patients and genotype-phenotype studies.

Iron-refractory iron-deficiency anemia (IRIDA) is a rare autosomal-recessive disorder characterized by hypochromic microcytic anemia, low transferrin saturation, and inappropriate high levels of the iron hormone hepcidin. The disease is caused by variants in the transmembrane protease serine 6 (TMPRSS6) gene that encodes the type II serine protease matriptase-2, a negative regulator of hepcidin transcription. Sequencing analysis of the TMPRSS6 gene in 21 new IRIDA patients from 16 families with different ethnic origin reveal 17 novel mutations, including the most frequent mutation in Southern Italy (p.W590R). Eight missense mutations were analyzed in vitro. All but the p.T287N variant impair matriptase-2 autoproteotylic activation, decrease the ability to cleave membrane HJV and inhibit the HJV-dependent hepcidin activation. Genotype-phenotype studies in IRIDA patients have been so far limited due to the relatively low number of described patients. Our genotype-phenotype correlation analysis demonstrates that patients carrying two nonsense mutations present a more severe anemia and microcytosis and higher hepcidin levels than the other patients. We confirm that TMPRSS6 mutations are spread along the gene and that mechanistically they fully or partially abrogate hepcidin inhibition. Genotyping IRIDA patients help in predicting IRIDA severity and may be useful for predicting response to iron treatment.