RESUMEN
Thalassaemia is caused by genetic globin defects leading to anaemia, transfusion-dependence and comorbidities. Reduced survival and systemic organ disease affect transfusion-dependent thalassaemia major and thalassaemia intermedia. Recent improvements in clinical management have reduced thalassaemia mortality. The therapeutic landscape of thalassaemia may soon include gene therapies as functional cures. An analysis of the adult US thalassaemia population has not been performed since the Thalassemia Clinical Research Network cohort study from 2000 to 2006. The Centers for Disease Control and Prevention supported US thalassaemia treatment centres (TTCs) to compile longitudinal information on individuals with thalassaemia. This dataset provided an opportunity to evaluate iron balance, chelation, comorbidities and demographics of adults with thalassaemia receiving care at TTCs. Two adult cohorts were compared: those over 40 years old (n = 75) and younger adults ages 18-39 (n = 201). The older adult cohort was characterized by higher numbers of iron-related comorbidities and transfusion-related complications. By contrast, younger adults had excess hepatic and cardiac iron and were receiving combination chelation therapy. The ethnic composition of the younger cohort was predominantly of Asian origin, reflecting the demographics of immigration. These findings demonstrate that comprehensive care and periodic surveys are needed to ensure optimal health and access to emerging therapies.
Asunto(s)
Talasemia/epidemiología , Adolescente , Adulto , Factores de Edad , Anciano , Anciano de 80 o más Años , Terapia Combinada/efectos adversos , Terapia Combinada/métodos , Comorbilidad , Manejo de la Enfermedad , Susceptibilidad a Enfermedades , Femenino , Predisposición Genética a la Enfermedad , Humanos , Sobrecarga de Hierro/diagnóstico , Sobrecarga de Hierro/etiología , Sobrecarga de Hierro/terapia , Masculino , Persona de Mediana Edad , Vigilancia en Salud Pública , Estudios Retrospectivos , Factores Sociodemográficos , Talasemia/diagnóstico , Talasemia/etiología , Talasemia/terapia , Estados Unidos/epidemiología , Adulto JovenRESUMEN
An international, multicenter registry was established to collect retrospective and prospective clinical data on patients with pyruvate kinase (PK) deficiency, the most common glycolytic defect causing congenital nonspherocytic hemolytic anemia. Medical history and laboratory and radiologic data were retrospectively collected at enrollment for 254 patients with molecularly confirmed PK deficiency. Perinatal complications were common, including anemia that required transfusions, hyperbilirubinemia, hydrops, and prematurity. Nearly all newborns were treated with phototherapy (93%), and many were treated with exchange transfusions (46%). Children age 5 years and younger were often transfused until splenectomy. Splenectomy (150 [59%] of 254 patients) was associated with a median increase in hemoglobin of 1.6 g/dL and a decreased transfusion burden in 90% of patients. Predictors of a response to splenectomy included higher presplenectomy hemoglobin (P = .007), lower indirect bilirubin (P = .005), and missense PKLR mutations (P = .0017). Postsplenectomy thrombosis was reported in 11% of patients. The most frequent complications included iron overload (48%) and gallstones (45%), but other complications such as aplastic crises, osteopenia/bone fragility, extramedullary hematopoiesis, postsplenectomy sepsis, pulmonary hypertension, and leg ulcers were not uncommon. Overall, 87 (34%) of 254 patients had both a splenectomy and cholecystectomy. In those who had a splenectomy without simultaneous cholecystectomy, 48% later required a cholecystectomy. Although the risk of complications increases with severity of anemia and a genotype-phenotype relationship was observed, complications were common in all patients with PK deficiency. Diagnostic testing for PK deficiency should be considered in patients with apparent congenital hemolytic anemia and close monitoring for iron overload, gallstones, and other complications is needed regardless of baseline hemoglobin. This trial was registered at www.clinicaltrials.gov as #NCT02053480.
Asunto(s)
Anemia Hemolítica Congénita no Esferocítica/diagnóstico , Estudios de Asociación Genética , Piruvato Quinasa/deficiencia , Errores Innatos del Metabolismo del Piruvato/diagnóstico , Adolescente , Adulto , Anemia Hemolítica Congénita no Esferocítica/etiología , Anemia Hemolítica Congénita no Esferocítica/metabolismo , Anemia Hemolítica Congénita no Esferocítica/terapia , Transfusión Sanguínea , Niño , Preescolar , Colecistectomía/efectos adversos , Colecistectomía/métodos , Terapia Combinada , Activación Enzimática , Femenino , Genotipo , Humanos , Lactante , Recién Nacido , Masculino , Persona de Mediana Edad , Mutación , Fenotipo , Piruvato Quinasa/metabolismo , Errores Innatos del Metabolismo del Piruvato/etiología , Errores Innatos del Metabolismo del Piruvato/metabolismo , Errores Innatos del Metabolismo del Piruvato/terapia , Esplenectomía/efectos adversos , Esplenectomía/métodos , Evaluación de Síntomas , Resultado del Tratamiento , Adulto JovenRESUMEN
Our phase I, open-label, multi-center, dose-escalation study evaluated the pharmacokinetics (PK) of SP-420, a tridentate oral iron chelating agent of the desferrithiocin class, in patients with transfusion dependent ß-thalassemia. SP-420 was administered as a single dose of 1.5 (n = 3), 3 (n = 3), 6 (n = 3), 12 (n = 3), and 24 (n = 6) mg/kg or as a twice-daily dose of 9 mg/kg (n = 6) over 14-28 days. There was a near dose-linear increase in the mean plasma SP-420 concentrations and in the mean values for Cmax and AUC0-τ over the dose range evaluated. The median tmax ranged from 0.5 to 2.25 h and was not dose dependent. The study was prematurely terminated by the sponsor due to renal adverse events (AE) including proteinuria, increase in serum creatinine, and one case of Fanconi syndrome. Other adverse effects included hypersensitivity reactions and gastrointestinal disturbances. Based on current dose administration, the renal AE observed outweighed the possible benefits from chelation therapy. However, additional studies assessing efficacy and safety of lower doses or less frequent dosing of SP-420 over longer durations with close monitoring would be necessary to better explain the findings of our study and characterize the safety of the study drug.
Asunto(s)
Ciclohexanonas/farmacocinética , Dihidropiridinas/efectos adversos , Quelantes del Hierro/efectos adversos , Quelantes del Hierro/farmacocinética , Tiazoles/efectos adversos , Tiazoles/farmacocinética , Talasemia beta/terapia , Adolescente , Adulto , Transfusión Sanguínea , Ciclohexanonas/efectos adversos , Ciclohexanonas/uso terapéutico , Dihidropiridinas/uso terapéutico , Relación Dosis-Respuesta a Droga , Humanos , Quelantes del Hierro/administración & dosificación , Enfermedades Renales/inducido químicamente , Persona de Mediana Edad , Sideróforos/uso terapéutico , Sideróforos/toxicidad , Tiazoles/uso terapéutico , Adulto Joven , Talasemia beta/complicaciones , Talasemia beta/tratamiento farmacológicoRESUMEN
BACKGROUND: Intestinal failure-associated liver disease (IFALD) can be treated with parenteral fish oil (FO) monotherapy, but practitioners have raised concerns about a potential bleeding risk. This study aims to describe the incidence of clinically significant post-procedural bleeding (CSPPB) in children receiving FO monotherapy. METHODS: A retrospective chart review was performed on patients at our institution treated with intravenous FO for IFALD. CSPPB was defined as bleeding leading to re-operation, transfer to the intensive care unit, re-admission, or death, up to one month after any invasive procedure. RESULTS: From 244 patients reviewed, 183 underwent ≥1 invasive procedure(s) (n = 732). Five (0.68%, 95% CI 0.22-1.59%) procedures resulted in CSPPB. FO therapy was never interrupted. No deaths due to bleeding occurred. CONCLUSIONS: Findings suggest that FO therapy is safe, with a CSPPB risk no greater than that reported in the general population. O3FA should not be held in preparation for procedures or in the event of bleeding.
Asunto(s)
Aceites de Pescado/administración & dosificación , Aceites de Pescado/efectos adversos , Hemorragia Gastrointestinal/etiología , Enfermedades Intestinales/tratamiento farmacológico , Fallo Hepático/tratamiento farmacológico , Emulsiones Grasas Intravenosas , Femenino , Hemorragia Gastrointestinal/epidemiología , Humanos , Incidencia , Lactante , Infusiones Intravenosas/efectos adversos , Masculino , Estudios Retrospectivos , Factores de RiesgoRESUMEN
Over the last several decades, our understanding of the genetic variation, pathophysiology, and complications of the hemolytic anemia associated with red cell pyruvate kinase deficiency (PKD) has expanded. Nonetheless, there remain significant gaps in our knowledge with regard to clinical care and monitoring. Treatment remains supportive with phototherapy and/or exchange transfusion in the newborn period, regular or intermittent red cell transfusions in children and adults, and splenectomy to decrease transfusion requirements and/or anemia related symptoms. In this article, we review the clinical diversity of PKD, the current standard of treatment and for supportive care, the complications observed, and future treatment directions.
Asunto(s)
Anemia Hemolítica Congénita no Esferocítica/terapia , Transfusión de Eritrocitos , Recambio Total de Sangre , Piruvato Quinasa/deficiencia , Errores Innatos del Metabolismo del Piruvato/terapia , Adulto , Anemia Hemolítica Congénita no Esferocítica/enzimología , Anemia Hemolítica Congénita no Esferocítica/patología , Anemia Hemolítica Congénita no Esferocítica/cirugía , Niño , Manejo de la Enfermedad , Humanos , Recién Nacido , Fototerapia , Errores Innatos del Metabolismo del Piruvato/enzimología , Errores Innatos del Metabolismo del Piruvato/patología , Errores Innatos del Metabolismo del Piruvato/cirugía , EsplenectomíaRESUMEN
PURPOSE: Thalassemia, a chronic blood disease, necessitates life-long adherence to blood transfusions and chelation therapy to reduce iron overload. We examine stability of health-related quality of life (HRQOL) in thalassemia and adherence to chelation therapy over time, especially after changes in chelator choice. METHODS: Thalassemia Longitudinal Cohort participants in the USA, UK, and Canada completed the SF-36v2 (ages 14+) and the PF-28 CHQ (parents of children <14 years). Chelation adherence was defined as self-reported percent of doses administered in the last 4 weeks. RESULTS: Two hundred and fifty-eight adults/adolescents (mean 29.7 years) and 133 children (mean 8.5 years) completed a mean of 2.8-years follow-up. Children made few chelator changes, whereas a mean of 2.2 changes was observed among the 37% of adults/adolescents who made chelator changes, mainly due to patient preference or medical necessity. Physical HRQOL improved among those with lower iron burden (better health status) at baseline who made a single change in chelator, but declined among participants with multiple changes and/or high iron burden (worse health status). Mental health improved among participants with lower iron burden, but iron overload was negatively associated with social functioning. Adherence did not significantly change over follow-up except for an increase after a change from deferoxamine (DFO) infusion to oral deferasirox (p = 0.03). Predictors of lower adherence for adults/adolescents at follow-up included side effects, smoking, younger age, problems preparing DFO, increased number of days per week DFO prescribed, and lower physical quality of life . CONCLUSIONS: Strategies to balance medical needs with family, work, and personal life may assist in adherence.
Asunto(s)
Quelantes del Hierro/administración & dosificación , Cumplimiento de la Medicación/estadística & datos numéricos , Calidad de Vida/psicología , Talasemia/tratamiento farmacológico , Adolescente , Adulto , Terapia por Quelación , Niño , Preescolar , Enfermedad Crónica , Estudios de Cohortes , Femenino , Humanos , Lactante , Sobrecarga de Hierro/tratamiento farmacológico , Sobrecarga de Hierro/etiología , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Talasemia/metabolismo , Adulto JovenRESUMEN
This exploratory study assessed apoptosis in peripheral blood leucocytes (PBL) from ß-thalassaemia patients receiving chronic transfusions and chelation therapy (deferasirox or deferoxamine) at baseline, 1, 6, and 12 months. At baseline, thalassaemic PBLs presented 50% greater levels of Bax (BAX), 75% higher caspase-3/7, 48% higher caspase-8 and 88% higher caspase-9 activities and 428% more nucleosomal DNA fragmentation than control subjects. Only neutrophils correlated significantly with apoptotic markers. Previously, we showed that over the treatment year, hepatic iron declined; we now show that the ratio of Bax/Bcl-2 (BCL2), (-27·3%/year), and caspase-9 activity (-13·3%/year) declined in both treatment groups, suggesting that chelation decreases body iron and indicators of PBL apoptosis.
Asunto(s)
Apoptosis , Leucocitos/metabolismo , Talasemia beta/metabolismo , Adolescente , Adulto , Transfusión Sanguínea , Caspasas/metabolismo , Terapia por Quelación , Niño , Preescolar , Fragmentación del ADN , Femenino , Humanos , Masculino , Adulto Joven , Proteína X Asociada a bcl-2/metabolismo , Talasemia beta/terapiaRESUMEN
BACKGROUND: Understanding patients' views about medication is crucial to maximize adherence. Thalassemia is a congenital blood disorder requiring chronic blood transfusions and daily iron chelation therapy. METHODS: The Beliefs in Medicine Questionnaire (BMQ) was used to assess beliefs in chelation in thalassemia patients from North America and London in the Thalassemia Longitudinal Cohort (TLC) of the Thalassemia Clinical Research Network (TCRN). Chelation adherence was based on patient report of doses administered out of those prescribed in the last four weeks. RESULTS: Of 371 patients (ages 5-58y, mean 24y), 93% were transfused and 92% receiving chelation (26% deferoxamine (DFO; a slow subcutaneous infusion via portable pump), 63% oral, 11% combination). Patients expressed high "necessity" for transfusion (96%), DFO chelation (92%) and oral chelation (89%), with lower "concern" about treatment (48%, 39%, 19% respectively). Concern about oral chelation was significantly lower than that of DFO (p<0.001). Self-reported adherence to chelation was not associated with views about necessity or concerns, but negatively correlated with perceived sensitivity to DFO (Sensitive Soma scale; r=-0.23, p=0.01) and side effects of oral chelation (r=-0.14, p=0.04). High ferritin iron levels, potentially indicating lower adherence, were found in 41% of patients reporting low necessity of oral chelation compared to 24% reporting high necessity (p=0.048). Concerns about treatment were associated with lower quality of life and more symptoms of anxiety and depression. CONCLUSIONS: Despite their requirement for multimodal therapy, thalassemia patients have positive views about medicine, more so than in other disease populations. Patients may benefit from education about the tolerability of chelation and strategies to effectively cope with side effects, both of which might be beneficial in lowering body iron burden. CLINICALTRIALS.GOV IDENTIFIER: NCT00661804.
Asunto(s)
Terapia por Quelación , Deferoxamina/uso terapéutico , Conocimientos, Actitudes y Práctica en Salud , Sideróforos/uso terapéutico , Talasemia/tratamiento farmacológico , Adolescente , Adulto , Niño , Preescolar , Femenino , Ferritinas/sangre , Humanos , Londres , Estudios Longitudinales , Masculino , Cumplimiento de la Medicación , Persona de Mediana Edad , América del Norte , Encuestas y Cuestionarios , Talasemia/psicología , Adulto JovenRESUMEN
BACKGROUND: Patients with thalassemia have low circulating levels of many nutrients, but the contribution of dietary intake has not been assessed. OBJECTIVE: Our objective was to assess dietary intake in a large contemporary sample of subjects with thalassemia. DESIGN: A prospective, longitudinal cohort study using a validated food frequency questionnaire was conducted. PARTICIPANTS/SETTING: Two hundred and twenty-one subjects (19.7±11.3 years, 106 were female) were categorized into the following age groups: young children (3 to 7.9 years), older children/adolescents (8 to 18.9 years), and adults (19 years or older); 78.8% had ß-thalassemia and 90% were chronically transfused. This study took place at 10 hematology outpatient clinics in the United States and Canada. MAIN OUTCOME MEASURES: We conducted a comparison of intake with US Dietary Reference Intakes and correlated dietary intake of vitamin D with serum 25-OH vitamin D and dietary iron with total body iron stores. STATISTICAL ANALYSES PERFORMED: Intake was defined as inadequate if it was less than the estimated average requirement. χ(2), Fisher's exact, and Student's t test were used to compare intake between age categories and logistic regression analysis to test the relationship between intake and outcomes, controlling for age, sex, and race. RESULTS: More than 30% of subjects consumed inadequate levels of vitamin A, D, E, K, folate, calcium, and magnesium. The only nutrients for which >90% of subjects consumed adequate amounts were riboflavin, vitamin B-12, and selenium. Dietary inadequacy increased with increasing age group (P<0.01) for vitamins A, C, E, B-6, folate, thiamin, calcium, magnesium, and zinc. More than half of the sample took additional supplements of calcium and vitamin D, although circulating levels of 25-OH vitamin D remained insufficient in 61% of subjects. Dietary iron intake was not related to total body iron stores. CONCLUSIONS: Subjects with thalassemia have reduced intake of many key nutrients. These preliminary findings of dietary inadequacy are concerning and support the need for nutritional monitoring to determine which subjects are at greatest risk for nutritional deficiency. Future research should focus on the effect of dietary quality and nutritional status on health outcomes in thalassemia.
Asunto(s)
Dieta/estadística & datos numéricos , Hierro de la Dieta/administración & dosificación , Estado Nutricional , Talasemia/sangre , Vitamina D/administración & dosificación , Adolescente , Adulto , Factores de Edad , Transfusión Sanguínea , Niño , Preescolar , Estudios de Cohortes , Femenino , Humanos , Hierro/sangre , Hierro de la Dieta/metabolismo , Estudios Longitudinales , Masculino , Política Nutricional , Necesidades Nutricionales , Estudios Prospectivos , Vitamina D/sangre , Vitaminas/administración & dosificación , Vitaminas/sangre , Adulto JovenRESUMEN
The Thalassemia Clinical Research Network collected adherence information from 79 patients on deferoxamine and 186 on deferasirox from 2007 to 2009. Chelation adherence was defined as percent of doses administered in the last 4 weeks (patient report) out of those prescribed(chart review). Chelation history since 2002 was available for 97 patients currently on deferoxamine and 217 on deferasirox, with crude estimates of adherence from chart review. Self-reported adherence to both deferoxamine and deferasirox were quite high, with slightly higher adherence to the oral chelator (97 vs. 92%). Ninety percent of patients on deferasirox reported at least 90% adherence, compared with 75% of patients on deferoxamine. Adherence to both chelators was highest in children, followed by adolescents and older adults.Predictors of lower deferoxamine adherence were smoking in the past year, problems sticking themselves (adults only), problems wearing their pump, and fewer transfusions in the past year. Predictors of lower deferasirox adherence were bodily pain and depression. Switching chelators resulted in increased adherence, regardless of the direction of the switch, although switching from deferoxamine to deferasirox was far more common. As adherence to deferoxamine is higher than previously reported, it appears beneficial for patients to have a choice in chelators.
Asunto(s)
Benzoatos/uso terapéutico , Terapia por Quelación , Deferoxamina/uso terapéutico , Quelantes del Hierro/uso terapéutico , Cumplimiento de la Medicación , Talasemia/tratamiento farmacológico , Triazoles/uso terapéutico , Adolescente , Adulto , Factores de Edad , Benzoatos/efectos adversos , Terapia por Quelación/efectos adversos , Niño , Preescolar , Deferasirox , Deferoxamina/efectos adversos , Femenino , Humanos , Quelantes del Hierro/efectos adversos , Masculino , Registros Médicos , Persona de Mediana Edad , América del Norte , Estudios Retrospectivos , Autoinforme , Triazoles/efectos adversos , Reino Unido , Adulto JovenRESUMEN
Thalassemia is an inherited blood disorder that requires lifelong adherence to a complicated and burdensome medical regimen which could potentially impact emotional functioning of patients. The importance of understanding and promoting healthy emotional functioning is crucial not only to psychological well-being, but also to physical health as it has been shown to impact adherence to medical regimens [1-4]. The current study aimed to [1] determine the prevalence of depressive and anxiety symptoms in adolescent and adult patients with thalassemia; and [2] explore possible demographic, medical, and psychosocial correlates of these symptoms in 276 patients (14-58 years old, M age = 27.83; 52% female). Overall, most patients did not report experiencing significant symptoms of anxiety and depression (33% of participants indicated experiencing symptoms of anxiety and 11% symptoms of depression). Females and older patients were more likely to experience these symptoms than males and younger patients. Symptoms of anxiety and depression were positively associated with self-report of difficulty with adherence and negatively associated with quality of life. Given these findings, regular screening for anxiety and depression symptoms could help to identify at-risk individuals to provide them with appropriate psychological support with the goal of improving both emotional and physical health.
Asunto(s)
Ansiedad/epidemiología , Depresión/epidemiología , Talasemia/psicología , Adolescente , Adulto , Ansiedad/etnología , Ansiedad/etiología , Pueblo Asiatico/psicología , Transfusión Sanguínea/psicología , Canadá/epidemiología , Terapia por Quelación/psicología , Depresión/etnología , Depresión/etiología , Femenino , Estudios de Seguimiento , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Cooperación del Paciente , Calidad de Vida , Riesgo , Factores Sexuales , Talasemia/epidemiología , Talasemia/etnología , Talasemia/terapia , Reino Unido/epidemiología , Estados Unidos/epidemiología , Población Blanca/psicología , Adulto JovenRESUMEN
BACKGROUND: We assessed whether oxidant-stress and inflammation in beta-thalassemia could be controlled by the novel oral iron chelator deferasirox as effectively as by deferoxamine. DESIGN AND METHODS: Forty-nine subjects were enrolled from seven sites and studied at baseline, and after 1, 6, and 12 months of therapy. Malondialdehyde, protein carbonyls, vitamins E and C, total non-transferrin bound iron, transferrin saturation, C-reactive protein, cytokines, serum ferritin concentration and liver iron concentration were measured. RESULTS: Liver iron concentration and ferritin declined significantly in both treatment groups during the study. This paralleled a significant decline in the oxidative-stress marker malondialdehyde (deferasirox -22%/year, deferoxamine -28%/year, average decline p=0.006). The rates of decline did not differ between treatment groups. Malondialdehyde was higher in both treatment groups than in a group of 30 non-thalassemic controls (p < 0.001). The inflammatory marker high-sensitivity C-reactive protein decreased significantly only in the group receiving deferasirox (deferasirox -51%/year, deferoxamine +8.5%/year, p = 0.02). This result was confounded by a chance difference in the level of high-sensitivity C-reactive protein between the two groups at baseline, but analyses controlling for this difference suggested an equally large treatment effect. CONCLUSIONS: Iron chelation therapy with deferoxamine or with deferasirox was equally effective in decreasing iron burden and malondialdehyde. The possible differential effect of the two chelators on inflammation warrants further investigation.
Asunto(s)
Benzoatos/farmacología , Deferoxamina/farmacología , Quelantes del Hierro/farmacología , Oxidantes/metabolismo , Triazoles/farmacología , Talasemia beta/tratamiento farmacológico , Adolescente , Adulto , Ácido Ascórbico/metabolismo , Benzoatos/efectos adversos , Proteína C-Reactiva/metabolismo , Niño , Deferasirox , Deferoxamina/efectos adversos , Femenino , Humanos , Quelantes del Hierro/efectos adversos , Peroxidación de Lípido , Masculino , Estrés Oxidativo , Triazoles/efectos adversos , Vitamina E/metabolismo , Talasemia beta/patologíaRESUMEN
Treatment of patients with beta-thalassemia major has improved dramatically during the past 40 years; however, the current clinical status of these patients remains poorly characterized. We performed a cross-sectional study of 342 patients in the Registry of the National Institutes of Health-sponsored Thalassemia Clinical Research Network. Evidence of hepatitis C exposure was present in 35% of tested patients, was associated with age, and had a rate of spontaneous viral clearance of 33%. Ferritin levels ranged from 147 to 11 010 ng/mL (median, 1696 ng/mL). Median hepatic iron content was 7.8 mg/g dry weight and 23% of patients had values of 15 mg/g dry weight or higher. No patients 15 years or younger and 5% of patients aged 16 to 24 years had heart disease requiring medication. Ten percent had cirrhosis on biopsy. Endocrinologic complications were common among adults. Seventy-four (22%) patients had recent implantable central venous access devices (CVADs) placed. Among 80 episodes of bacteremia in 38 patients, 90% were attributable to the CVAD. Among 330 patients who had received deferoxamine chelation therapy, 224 (68%) reported no complications. We conclude that hepatitis C, iron-related organ dysfunction, and complications of iron chelation therapy are strongly age-dependent in North American patients with beta-thalassemia.
Asunto(s)
Talasemia beta/complicaciones , Adolescente , Adulto , Factores de Edad , Niño , Preescolar , Estudios Transversales , Deferoxamina/efectos adversos , Enfermedades del Sistema Endocrino/epidemiología , Enfermedades del Sistema Endocrino/etiología , Ferritinas/sangre , Genotipo , Cardiopatías/epidemiología , Cardiopatías/etiología , Humanos , Lactante , Hierro/metabolismo , Quelantes del Hierro/efectos adversos , Quelantes del Hierro/uso terapéutico , Sobrecarga de Hierro/epidemiología , Hígado/química , Hígado/patología , Cirrosis Hepática/epidemiología , Cirrosis Hepática/etiología , Persona de Mediana Edad , Estudios Retrospectivos , Reacción a la Transfusión , Talasemia beta/sangre , Talasemia beta/epidemiología , Talasemia beta/terapiaRESUMEN
Fibroblasts from patients with thiamine-responsive megaloblastic anemia (TRMA) syndrome with diabetes and deafness undergo apoptotic cell death in the absence of supplemental thiamine in their cultures. The basis of megaloblastosis in these patients has not been determined. Here we use the stable [1,2-13C2]glucose isotope-based dynamic metabolic profiling technique to demonstrate that defective high-affinity thiamine transport primarily affects the synthesis of nucleic acid ribose via the nonoxidative branch of the pentose cycle. RNA ribose isolated from TRMA fibroblasts in thiamine-depleted cultures shows a time-dependent decrease in the fraction of ribose derived via transketolase, a thiamine-dependent enzyme in the pentose cycle. The fractional rate of de novo ribose synthesis from glucose is decreased several fold 2 to 4 days after removal of thiamine from the culture medium. No such metabolic changes are observed in wild-type fibroblasts or in TRMA mutant cells in thiamine-containing medium. Fluxes through glycolysis are similar in TRMA versus control fibroblasts in the pentose and TCA cycles. We conclude that reduced nucleic acid production through impaired transketolase catalysis is the underlying biochemical disturbance that likely induces cell cycle arrest or apoptosis in bone marrow cells and leads to the TRMA syndrome in patients with defective high-affinity thiamine transport.