Transfusing children with hemoglobinopathies.

Thalassemia and sickle cell disease (SCD) are among the most common inherited diseases worldwide. Red blood cell transfusion is a cornerstone of their treatment, but its indications have significantly changed over the past years. New therapies are emerging in both syndromes: among them, hematopoietic stem cell transplantation is now routinely proposed, and gene therapy has shown promising preliminary results.

Management of iron overload in hemoglobinopathies.

Hemoglobinopathies, thalassemia and sickle cell disease are among the most frequent monogenic diseases in the world. Transfusion has improved dramatically their prognosis, but provokes iron overload, which induces multiple organ damages. Iron overload is related to accumulation of iron released from hemolysis and transfused red cell, but also, in thalassemic patients, secondary to ineffective erythropoiesis, which increases intestinal iron absorption via decreased hepcidin production. Transfusion-related cardiac iron overload remains a main cause of death in thalassemia in well-resourced countries, and is responsible for severe hepatic damages in sickle cell disease. Regular monitoring by Magnetic Resonance Imaging (MRI) using myocardial T2* (ms) and Liver Iron Content (LIC) (mg of iron/g dry weight) are now standards of care in chronically transfused patients. Serum ferritin level measurements and record of the total number of transfused erythrocyte concentrates are also helpful tools. Three iron chelators are currently available, deferoxamine, which must be injected subcutaneously or intravenously, and two oral chelators, deferiprone and deferasirox. We will review the main characteristics of these drugs and their indications.

[Cerebral vasculopathy in pediatric sickle-cell anemia]. / Drépanocytose et atteinte vasculaire cérébrale chez l'enfant.

In children with sickle-cell anemia, cerebral vasculopathy is a frequent and severe complication. It is attributed not only to erythrocyte sickling but also to multiple physiological modifications associated with sickle-cell anemia: platelet and leukocyte activation, endothelial injury and remodeling, coagulation activation, hemolysis and subsequent chronic inflammation, impaired vasomotricity, etc. Intracranial large-vessel remodeling leads to clinical cerebral infarction, whereas microvascular injury and impaired vasoreactivity lead to so-called silent infarcts, which are actually associated with impaired cognitive development. Primary prevention strategies have been developed to screen children for cerebral vasculopathy and to further reduce stroke risk. Annual transcranial Doppler beginning at 2 years of age is recommended, allowing risk stratification. Patients at high risk are enrolled in a monthly transfusion exchange program, which reduces the risk of a first stroke by 90 %. Chronic transfusion therapy has also demonstrated efficacy in preventing a second stroke, as a secondary prevention strategy. Lifelong treatment is recommended, as recurrent stroke has been observed when transfusion is discontinued. The burden of chronic transfusion is heavy for patients. Furthermore, several studies have shown that, despite preventing clinically symptomatic stroke, chronic transfusion therapy may not be effective concerning silent infarct progression. Other therapeutic options are currently being explored to obtain better protection with reduced side effects.

Cerebrovascular complications in children with sickle cell disease.

Cerebrovascular accidents were until recently responsible for much mortality and morbidity in children with sickle cell disease; the likelihood of a child with HbSS having a stroke was 11% before age 20 years, with a peak incidence of ischemic stroke between 2 and 5 years of age, and of hemorrhagic strokes between 20 and 29 years of age. Vessels occlusion is likely initiated by intimal proliferation and amplified by inflammation, excessive adhesion of cells to activated endothelium, hypercoagulable state, and vascular tone dysregulation. Silent infarcts may occur and are associated with decreased cognitive functions. Transcranial Doppler ultrasonography (TCD) was more recently demonstrated able to achieve early detection of the children at high risk for clinical strokes. A randomized study demonstrated that a first stroke may be prevented by monthly transfusion in children with abnormal TCD, leading to a recommendation for annual TCD screening of children aged between 2 and 16 years and monthly transfusion for those with abnormal results. In children who have had a first stroke, the risk of recurrence is more than 50% and is greatly reduced by chronic transfusion, although not completely abolished. Hematopoietic stem cell transplant is indicated in children with cerebral vasculopathy who have an HLA-identical sibling.

[Is therapeutic progress in the management of sickle cell disease applicable in sub-Saharan Africa?]. / Les progrès thérapeutiques dans la prise en charge de la drépanocytose sont-ils applicables en Afrique subsaharienne?

The life expectancy of patients with sickle cell disease has improved in the United States and Europe thanks to the use of penicillin prophylaxis, appropriate immunizations, neonatal screening, implementation of a quality transfusional policy, hydroxyurea therapy, detection and treatment of cerebral vasculopathy, recognition of situations that can benefit from allogenic marrow transplantation, and improvements in bone marrow transplantation techniques. The cost of almost all these techniques is far beyond the means of health care systems in Africa where they cannot be used. However at least three, i.e., penicillin, vaccines, and hydroxyurea, could be easily accessible in the framework of defined therapeutic strategies. If daily penicillin and pneumococcal vaccine Pneumo 23 are required, it would likely be necessary to select a conjugated vaccine other than Prevenar that does not provide protection against all strains present in Africa. Neonatal screening is still a rare procedure in sub-Saharan countries. Periodic transfusion is steadily improving but exchange transfusion programs aimed in particular at preventing neurological complications are still unfeasible. Indications for hydroxyurea therapy in Africa are more common due to the lack of access to chronic transfusion and must be based on consensus decision. Use of bone marrow transplantation, i.e., the only currently available curative treatment, is still possible only in northern hemisphere countries where it is still restricted to children with severe forms and an HLA-compatible family donor.

Antibiotic prevention of pneumococcal infections in asplenic hosts: admission of insufficiency.

Asplenic and hyposplenic patients have an increased risk for overwhelming pneumococcal infections, even several decades after splenectomy. Pneumococcal vaccination and daily oral administration of penicillin V are recommended to prevent such infections, 2-5 years after splenectomy, and for at least 5 years in children affected with sickle cell disease. In order to assess whether the infectious risk is actually known and prevented, we interviewed physicians (belonging to a general practitioner and pediatrician network) who followed patients having undergone a splenectomy and/or children with sickle cell disease under 5 years of age. We received replies from 104 physicians monitoring 152 patients replied. Potential infection risk was not known for 28% of the asplenic patients and 40% of the children with sickle cell disease. Only 75% of the asplenic patients and 36% of the children with sickle cell disease had been vaccinated against pneumococcus. Of the patients who had undergone splenectomy, 27% had been treated with an antibiotic after surgery and 60% had discontinued it, the vast majority of them during the same year. Of the children with sickle cell disease, 48% were not receiving an antibiotic. This study demonstrates that risk of infections in asplenic patients is widely misunderstood, indicating the urgent need to improve their management.

[Transfusion in patients with hemoglobinopathies]. / Transfusion des patients atteints d'hémoglobinopathies.

A-Thalassemia involves a production deficiency concerning the synthesis of alpha-globin chains, and beta-thalassemia involves the beta-globin chains. Only a few patients in France are affected by the major form of thalassemia (certain types of homozygotic beta-thalassemia). Also, the systematic screening of 'at-risk' couples and prenatal diagnosis has helped to considerably reduce the incidence of new cases. The decision to perform regular blood transfusions is made when Hb levels fall below values that are compatible with normal activity. Hb levels above 10 g/dL permit normal educational, recreational and professional activity. This level is generally maintained via a 15 mL/kg erythrocyte concentrate supplement every three weeks, or 20 mL/kg every four weeks. However, the appearance of antierythrocytic autoantibodies is possible, and this may also result in an increase in blood transfusion requirements. In intermediate thalassemia patients, residual Hb levels are maintained at between 7 and 10 g/dL, and transfusion of erythrocyte concentrates is only made in the case of aggravation of chronic anemia or when there are signs of intolerance to chronic anemia. In France, there is relatively large population of patients with sickle cell disease. Blood transfusion is a major element in the treatment of these patients. Simple transfusion is performed in cases of a lack of iron or folates, increased hemolysis, splenic sequestration or parvovirus 19 infection. The target hematocrit should mostly remain at the patient's baseline value. Exchange transfusions are not performed on a regular basis, but only in cases of stroke or other severe vaso-occlusive events, or when a patient has to be prepared for surgery. A minority of subjects are involved in chronic blood transfusion, which is used mostly to prevent cerebrovascular accidents but also in cases of cardiac, renal, or respiratory insufficiency. There is an increased prevalence of antierythrocytic alloimmunization in sickle cell patients, most probably because of the discrepancies in red cell antigens between mainly Caucasian blood donors and Afro-Caribbean recipients.

Preliminary report of a toxicity study of hydroxyurea in sickle cell disease. French Study Group on Sickle Cell Disease.

AIM: To evaluate the tolerance of hydroxyurea in children affected with sickle cell disease. DESIGN: Questionnaire study of French physicians likely to treat patients with sickle cell disease. Data were collected on 101 children with sickle cell disease, treated for a median of 22 months, 36 of whom were treated for more than three years. 13 children were younger than 5 years of age at inclusion. RESULTS: Hydroxyurea was stopped for medical reasons in 11 patients: 6 failures, 1 pregnancy, 1 cutaneous rash, 1 leg ulcer, 1 lupus. Acute lymphoblastic leukaemia occurred in a girl treated for 1.5 months with hydroxyurea, this short interval arguing against a causative association. One 17 year old boy had paraparesis after 8 years of treatment. CONCLUSIONS: No major short or medium term toxicity was related to hydroxyurea in this cohort of 101 children. However, the number of children treated for more than 3 years is too few to make firm conclusions on the long term tolerance of this drug.

[Iron chelation in 1998]. / La chélation du fer en 1998.

Chronic transfusion regimens lead inevitably to iron overload, causing progressive organ dysfunctions and limiting life expectancy, so that iron chelation is needed in multiple-transfused patients to reduce iron accumulation and toxicity. Desferal is still the most used and the most efficacious chelator. It must be, however, administered through subcutaneous infusion over 8-12 hours. Difficulties with compliance have prompted an ongoing search for alternatives, and in particular for molecules active after oral administration. The only drug available today is L1. This drug is less active than Desferal, and is responsible for rare agranulocytosis. Its indications are still to be discussed.

Three-year follow-up of hydroxyurea treatment in severely ill children with sickle cell disease. The French Study Group on Sickle Cell Disease.

PURPOSE: To observe the safety and efficacy of hydroxyurea (HU), a drug that stimulates fetal hemoglobin (Hb F) production, in previously severely ill children with sickle cell disease. PATIENTS AND METHODS: HU was given in an uncontrolled study to 35 children with sickle cell disease, aged from 3 to 20 years, suffering from frequent painful crises. Mean duration of treatment was 32 months (range: 12-59 months). RESULTS: HU induced an increase in Hb F levels in all children out one; this increase was maximal after 9 months of treatment, was largely sustained thereafter, and was related to HU dose and inversely to patients' age. We also noted an apparent reduction in crisis, which occurred principally after 3 months of therapy and did not seem strictly correlated with the rise in Hb F level. No serious hematopoietic complication was observed. Growth curves and sexual development were not modified. CONCLUSION: Our data support the efficacy of HU in reducing painful events in children with sickle cell disease. Short- and middle-term tolerances are good. Thus, we think that HU can be given to children affected by frequent and severe painful crises. We recommend, however, very cautious use of this drug, because its long-term effects in children are still unknown.

Autologous blood donation for elective surgery in children weighing 8-25 kg.

To determine whether autologous blood donation can be used safely and efficiently in children weighing 8-25 kg, we studied children whose perioperative blood losses were expected to exceed 25% of total blood volume. Blood donations were performed in pediatric units, under the direction of an anesthesiologist and a blood bank physician experienced in paediatric care. Twenty-four children, median age 6 years (1-13), were included. They underwent surgery mainly for digestive or urological disorders, and for orthopedic defects. Forty blood collections were performed of the 46 prescribed. Phlebotomies could not be performed in 1 child because of the mother's apprehension, and in 5 cases because of venous access problems. All phlebotomies were hemodynamically well tolerated. Hemodilution was also performed in 17 children, and cell saver used in 2. Allogeneic blood transfusion was avoided in 21/24 children.

Gadolinium-DOTA enhanced MRI of painful osseous crises in children with sickle cell anemia.

In order to evaluate the role of gadolinium-DOTA enhanced MRI in the management of painful osseous crises in children with sickle cell anemia (SCA), nine children with SCA underwent MRI, bone scans and ultrasonographic studies during 11 osseous crises. Imaging findings were compared with the final diagnosis: three acute osteomyelitis (AO) and 16 acute infarcts (AI). MRI could not differentiate AO from AI. The appearance of severe AI was very misleading and was similar to the usual appearance of AO, including soft tissue changes, periosteal reaction and patterns of enhancement. Gadolinium-DOTA enhanced MRI was useful for determining the anatomic site and extent of AO or AI and for distinguishing between necrotic material, fluid collection and vascularized inflammatory tissue. It can also help to guide the aspiration of intraosseous, subperiosteal and soft tissue fluid collections.

Human T-cell lymphotropic virus type I and II DNA amplification in seropositive and seronegative at-risk individuals.

To determine the presence or the absence of human T-lymphotropic virus type I and/or II (HTLV-I/II) DNA in at-risk individuals who were persistently negative for specific serologic assays, polymerase chain reaction with two primer pairs in common and conserved regions of HTLV-I and -II genomes was used. Seronegative individuals at risk for HTLV-I/II infection (15 heterosexual partners of seropositive individuals, 17 breastfed children born to HTLV-I-infected mothers, 47 multiply transfused patients, 22 intravenous drug users) were studied (n = 101); 35 seropositive individuals and 25 seronegative low-risk individuals were used as positive and negative controls, respectively. No positive polymerase chain reaction was observed in the seronegative at-risk individuals or in the negative controls. Positive controls gave positive results with at least one primer pair in all cases except one. A latent HTLV-I/II infection with a persistently negative serologic test for HTLV-I/II seems unlikely.

Molecular epidemiology of chronic pulmonary colonisation by Pseudomonas aeruginosa in cystic fibrosis.

The epidemiology of pulmonary colonisation by Pseudomonas aeruginosa was studied in 21 patients with cystic fibrosis (CF) by field inversion gel electrophoresis. DraI-DNA restriction patterns were analysed for 187 P. aeruginosa isolates from these patients. The results revealed that the strains present in individual patients varied during the course of chronic colonisation; the emergence of new strains often was associated with periods of antibiotic therapy. Patients often were colonised by more than one strain (two or three strains were present in 54% of the patients) and the strains obtained from unrelated patients were highly heterogeneous, in contrast to those isolated from a pair of twins. These results demonstrate the heterogeneity and variability of P. aeruginosa isolates in the pulmonary flora of chronically infected CF patients.