Thompson, Christineil

This Viewpoint summarizes recent progress in gene therapy for hemoglobinopathies.

ABSTRACTAthletes are at high risk of iron deficiency even without anemia. In this systematic review and meta‐analysis that included 17,519 athletes in 122 references from 23 countries, participating in 62 unique sports over a 41‐year timeframe, approximately 53.9% of student‐athletes were found to be hypoferritinemic (ferritin concentration below 50 mcg/L) with 23.0% percent showing absolute iron deficiency based on current definitions (ferritin concentration below 20 mcg/L). These findings strongly suggest that changes in clinical practice guidelines are warranted to enable routine screening for iron deficiency among adolescent and collegiate athletes.

ABSTRACTObjectiveIron and other biologically important metals are essential to mitochondrial function but are not routinely evaluated. Their equilibrium is critical to the optimal performance of cells with high metabolic activity such as neurons, cardiomyocytes, and skeletal myocytes. Teenagers are at a high risk of iron deficiency even without anemia. Metal ion imbalances can cause cognitive impairments, muscle weakness, and sudden cardiac death. We aim to assess the current prevalence of iron deficiency among collegiate athletes in the Upper Midwest.MethodsOur study is a multicenter, retrospective chart review of outpatient clinics in a regional healthcare system between January 2012 and December 2023, and a national public database between 2017 and March 2020. We reviewed the ferritin concentrations of regional collegiate athletes having preparticipation sport evaluations and nationally in the NHANES database.ResultsWe identified 643 unique individuals aged 16–21 years with 253 having ferritin screening. Iron deficiency (ferritin <20 mcg/L) was present in 24.5% and hypoferritinemia (ferritin <50 mcg/L) was present in 66.7% of collegiate athletes. From the NHANES database, 12.7% of active sampled participants aged 16–21 years were iron deficient.ConclusionOur study findings suggest the need for universal screening for iron deficiency among collegiate athletes given the high prevalence of iron deficiency in both the retrospective chart review and NHANES database analysis. Given the critical role of metal ion homeostasis to optimal mitochondrial function, these findings may warrant the inclusion of ferritin testing in cardiac, neurological, and skeletal muscle evaluations.

Background Low ferritin levels have been previously described to lower HbA 2 percentages on hemoglobinopathy evaluation. At our institution we have incorporated serum ferritin levels into an expanded panel test for thalassemia and hemoglobinopathy to assist with interpretation. There have been many critiques on the reference ranges used to define low ferritin in various pediatric ages. Lower ferritin levels, even in the absence of anemia or microcytosis, have been ascribed to nonspecific symptoms such as fatigue, weakness, difficulty concentrating, and decreased productivity that could be misconstrued as an attention-deficit disorder, especially in children. A hemoglobinopathy evaluation is often the first occasion for ferritin testing in patients; therefore, the hemoglobinopathy evaluation can serve as a key checkpoint to detect iron deficiency allowing for prompt treatment and amelioration of symptoms. Objective The purpose of this study was to evaluate the relationship between ferritin levels and the occurrence of hemoglobinopathies among pediatric patients in a single institution with the expectation that patients obtaining a hemoglobinopathy workup would be more likely to have a low ferritin (null hypothesis: there is no difference in the ferritin levels between patients receiving a hemoglobinopathy workup). The second hypothesis was that hemoglobinopathy testing would be done in a stepwise manner so at least 50% of patients obtaining a hemoglobinopathy workup would have prior interventions such as iron supplementation (null hypothesis: patients obtaining hemoglobinopathy evaluation have less prior interventions such as iron supplementation). Design/Method This retrospective, single center study included patients aged 0-18 years who had their first thalassemia and hemoglobinopathy testing for any indication between January 1, 2023 and July 28, 2023. Clinical variables were collected via review of the medical record. Low ferritin was defined as a ferritin level less than or equal to 25 mcg/L. Pearson's Chi Squared test and the Kruskal Wallis test were used for statistical analysis of categorical and continuous variables respectively. Results Seventy-seven total eligible patients were identified. Of those patients 35 were found to have low ferritin levels (45.5%). Among the patients with a low ferritin level, 15 patients also had a hemoglobinopathy present on their testing (41.7%) but there was no significant difference compared to those with normal ferritin levels (p value = 0.467). The patients with normal ferritin levels were of a significantly higher age compared to those with low ferritin levels 12.2 years vs 6.8 years (p value = 0.001) and 14 (42.4%) patients with low ferritin had no anemia and 29 (82.9%) never received prior iron supplementation. It was also noted that patients of Asian race were significantly more likely to have received prior iron supplementation 27.3% (p value = 0.004). Among patients with a hemoglobinopathy present the average age of their diagnosis was 9.1 years (95% Confidence Interval 6.6-11.7 years). Nine of the 10 patients with no hemoglobin values available were tested due to college sports participation and only 2 of those patients were found to have low ferritins. Conclusion Among our group of pediatric patients who underwent evaluation for thalassemia and hemoglobinopathy, there was no significant difference between those having a hemoglobinopathy present and lower or higher ferritin levels. Iron deficiency was more often noted among the younger patients even in the absence of anemia. It was important to note the majority of patients with iron deficiency detected on the hemoglobinopathy evaluation had never received prior iron supplementation until the time of their hemoglobinopathy evaluation. This also demonstrates that many providers may not do a stepwise workup but order all the evaluations at once. As there are many nonspecific symptoms of iron deficiency that can hinder the development of a child it is valuable to detect iron deficiency on hemoglobinopathy testing in order to intervene as soon as possible as iron deficiency can be masked by normal hemoglobin and normocytosis. Further investigation with larger study groups is warranted to better elucidate this relationship. Overall, our results suggest that enhanced characterization of iron deficiency parameters for patients receiving a hemoglobinopathy evaluation is warranted.

Abstract Background Large β-globin gene cluster deletions (hereditary persistence of fetal hemoglobin [Hb] or β-, δβ-, γδβ-, and ϵγδβ-thalassemia), are associated with widely disparate phenotypes, including variable degrees of microcytic anemia and Hb F levels. When present, increased Hb A2 is used as a surrogate marker for β-thalassemia. Notably, ϵγδβ-thalassemias lack the essential regulatory locus control region (LCR) and cause severe transient perinatal anemia but normal newborn screen (NBS) results and Hb A2 levels. Herein, we report a novel deletion of the ϵ, Aγ, Gγ, and ψβ loci with intact LCR, δ-, and β-regions in 2 women and newborn twins. Methods Capillary electrophoresis (CE), high-performance liquid chromatography (HPLC), DNA sequencing, multiplex ligation-dependent probe amplification (MLPA), gap-polymerase chain reaction (gap-PCR), and long-read sequencing (LRS) were performed. Results NBS showed an Hb A &gt; Hb F pattern for both twins. At 20 months, Hb A2 was increased similarly to that in the mother and an unrelated woman. Unexplained microcytosis was absent and the twins lacked severe neonatal anemia. MLPA, LRS, and gap-PCR confirmed a 32 599 base pair deletion of ϵ (HBE1) through ψβ (HBBP1) loci. Conclusions This deletion represents a hemoglobinopathy category with a distinct phenotype that has not been previously described, an ϵγ-thalassemia. Both the NBS Hb A &gt; F pattern and the subsequent increased Hb A2 without microcytosis are unusual. A similar deletion should be considered when this pattern is encountered and appropriate test methods selected for detection. Knowledge of the clinical impact of this new category will improve genetic counselling, with distinction from the severe transient anemia associated with ϵγδβ-thalassemia.

Abstract The εγδβ thalassemias (EGDBT) are infrequently occurring deletions of the β globin gene cluster on chromosome 11. EGDBTs can be an unsuspected cause of severe neonatal anemia that resolves during the first year of life into a normal Hb A2 thalassemic phenotype, presumed to be due to an imbalance of β-like chains during development. First described in 1972, they are categorized into two groups, both with loss of the five DNase I hypersensitivity sites upstream of the β gene (HBB) called the locus control region (LCR). In group 1 deletions, all or most of the β globin gene cluster including HBB is deleted; in group 2 deletions, removal of the LCR silences an intact HBB. Large deletions that do not involve LCR but remove the embryonic (HBE) and fetal genes (HBG2/HBG1) [LCR(ε Gγ Aγ) 0δβ] have not been reported. It is not known whether a deletion with intact LCR as well as δ and β genes would similarly manifest as neonatal anemia that resolves into a normocytic phenotype with normal hemoglobin fraction percentages after infancy. Four individuals with an LCR(ε Gγ Aγ) 0δβ deletion have been evaluated. These include monochorionic, diamniotic twin girls whose newborn screen (NBS) returned significant for Hb A percentage greater than Hb F for both twins. NBS was repeated two weeks later with the same result. The newborns were induced late pre-term (36 weeks and 6 days) after an uncomplicated pregnancy, including no features of twin to twin transfusion. Both infants had no anemia and bilirubin levels remained in the low to low-intermediate risk zones. Neither twin received transfusions or phototherapy during admission. At a follow up visit at 20 months of age a hemoglobin electrophoresis was performed which showed borderline Hb A2 and no Hb F in both twins (Table 1). Ferritin levels were low-normal in Twin A (14 µg/L) and low in Twin B (9 µg/L). Both infants were found to have a heterozygous large deletion affecting HBE, HBG2, HBG1, and HBBP1 loci by Multiplex Ligation-dependent Probe Amplification (MLPA), a method that uses multiple DNA probe pairs to determine the size of the DNA segment deleted. MLPA deletion/duplication testing on the α genes was negative. No β globin variants were identified by DNA sequencing. An evaluation was performed on the 25 year-old healthy mother and showed similar findings including the heterozygous large deletion. Mother and infants continue to be asymptomatic with normal red cell indices for age (Table 1). The fourth was an unrelated 40-year-old female with mild anemia screened by hemoglobin electrophoresis for obstetric evaluation who was found to have borderline Hb A2 (see table 1). MLPA showed a heterozygous deletion involving the same loci. Again, no β globin variants were identified by DNA sequencing. All four cases showed the same MLPA pattern except one non-specific probe commonly altered in common gamma gene conversion events. Long range sequencing performed on one case confirmed a single contiguous 32,599 bp deletion that matched the MLPA data (g.5262276-5294875). The detected deletion has not been reported in literature and differs from EGDBT mutations in that the LCR is intact. As the LCR controls expression of the entire gene cluster, this mutation is expected to display different phenotypic features than classic EGDBT. HBD and HBB are not deleted and therefore adequate transcription of Hb A2 and Hb A are expected with no imbalance of α/β chains after the neonatal period. It is postulated this finding explains the decreased Hb F levels in the NBS test result. The Hb A2 increase is likely a product of this deletion and does not indicate β-thalassemia. The heterozygous absence of HBE and HBG2/HBG1 may result in upregulation of HBD and HBB expression through loss of FKLF and FKLF-2 binding. In addition, HBB-EKLF binding would have less competition as the gamma promoter elements have been heterozygously deleted. In summary, in contrast to classic EGDBTs which cause transient severe neonatal anemia and resolve to normal Hb A2 thalassemic indices, this novel LCR(ε Gγ Aγ) 0δβ deletion was associated with normal CBC values with an absence of severe neonatal anemia, inverted Hb F/Hb A percentages at birth and borderline Hb A2 levels. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.