Hydroxyurea: an alternative to transfusion therapy for stroke in sickle cell anemia

Blood Transfusion Vs. Hydroxyurea for Stroke Prevention in Children With Sickle Cell Anemia: A Systematic Review and Meta-Analysis

Sickle cell anemia (SCA) is a hereditary condition that can lead to severe complications in children such as acute coronary syndrome, splenic sequestration, renal failure, and stroke. Blood transfusion and hydroxyurea (HU) therapy are used to prevent stroke in children with sickle cell disease (SCD). Preliminary data show considerable variation and inconsistency in the use of these two therapeutic interventions. Therefore, this systematic review was carried out to compare the effects of blood transfusion to HU therapy in preventing stroke for children with sickle cell disease. There was an extensive literature search in reliable and authentic databases like PubMed, Medline, Scopus, Cochrane, and Science Direct to obtain relevant articles. This study used the standards and guidelines from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). During the systematic review, data were obtained focusing on the following parameters: the size of the sample in the study, the age of the subjects involved in the study, the type of Intervention, and the outcome. After an initial search of 163 papers, 25 studies were included. The results of the research give the first evidence that HU is effective in the treatment of cerebrovascular problems in children with SCD. However, it is unclear under what circumstances HU may prevent a second stroke. It can be concluded that children with SCA can effectively avoid primary strokes through chronic blood transfusions and HU.

Lower Transcranial Doppler Flow Velocities in Sickle Cell Anemia Patients on Hydroxyurea: Myth or Fact

Transcranial Doppler (TCD) detects stroke risk in patients with sickle cell anemia (SCA). Hydroxyurea therapy has the ability to induce increased levels of fetal hemoglobin in sickle cells thus decreasing tendency for red cell sickling. This study aimed to evaluate TCD findings in SCA patients on hydroxyurea and correlate the time-averaged mean velocity (TAMV) with their hematological parameters. Forty SCA patients of both sexes, aged 16-22 years with no history of stroke were screened with TCD for an elevated TAMV, divided into: Group T (20 patients on blood transfusion); and Group H (20 patients on daily hydroxyurea). For all, full medical history, clinical examination, hemoglobin, hematocrit, leukocytes, platelets, fetal hemoglobin and sickling test, in addition TCD to describe the pattern of cerebral blood flow abnormalities were done. TAMV in all cerebral arteries were significantly higher in Group T than Group H, the highest TAMV (147.5 ± 57.09 cm/s) was found in the right middle cerebral artery and correlated negatively with hematocrit in Groups H (P < 0.001). There were 2 (10%) abnormal TAMV results and 5 (25%) conditional in Group T, while all results were normal in Group H. Hydroxyurea therapy may lower TCD velocities and prevent the risk of primary stroke in SCA patients.

Sickle cell disease: new opportunities and challenges in Africa

Sickle cell disease (SCD) is one of the most common genetic causes of illness and death in the world. This is a review of SCD in Africa, which bears the highest burden of disease. The first section provides an introduction to the molecular basis of SCD and the pathophysiological mechanism of selected clinical events. The second section discusses the epidemiology of the disease (prevalence, morbidity, and mortality), at global level and within Africa. The third section discusses the laboratory diagnosis and management of SCD, emphasizing strategies that been have proven to be effective in areas with limited resources. Throughout the review, specific activities that require evidence to guide healthcare in Africa, as well as strategic areas for further research, will be highlighted.

Hemodynamic responses to visual stimulation in children with sickle cell anemia

Blood oxygenation level-dependent (BOLD) and cerebral blood flow (CBF)-based functional magnetic resonance imaging (fMRI) were used to measure primary visual cortex responses to photic stimulation in 23 children (12.4  ±  0.7 years old) with sickle cell anemia (SCA) and 21 clinical controls (11  ±  1.0 years old). The objectives were to investigate the effect of SCA on detection of brain activation with fMRI and to explore the relationship between fMRI responses and global cognitive function. The BOLD responses were diminished in children with SCA. Clinical indicators of disease severity were greatest in patients without detectable visual cortex activation, but blood hemoglobin concentration and resting CBF were not predictive of BOLD signal amplitude in the SCA patients. Unexpectedly, the BOLD signal amplitude was positively associated (r(s)  ≥  0.8, p  ≤  0.05) with Wechsler Abbreviated Scale of Intelligence scores, suggesting that fMRI may help clarify medical, hemodynamic, and neural factors that mediate adverse effects of SCA on neurocognitive function.

Stroke With Transfusions Changing to Hydroxyurea (SWiTCH)

Stroke is a devastating complication of sickle cell anemia (SCA) with high recurrence if untreated. Chronic transfusions reduce recurrent strokes but have associated morbidities including iron overload. Stroke With Transfusions Changing to Hydroxyurea (SWiTCH) was a multicenter phase 3 randomized trial comparing standard treatment (transfusions/chelation) to alternative treatment (hydroxyurea/phlebotomy) for children with SCA, stroke, and iron overload. SWiTCH was a noninferiority trial with a composite primary end point, allowing an increased stroke risk but requiring superiority for removing iron. Subjects on standard treatment received monthly transfusions plus daily deferasirox iron chelation. Subjects on alternative treatment received hydroxyurea plus overlap transfusions during dose escalation to maximum tolerated dose (MTD), followed by monthly phlebotomy. Subjects on standard treatment (N = 66) maintained 30% sickle hemoglobin (HbS) and tolerated deferasirox at 28.2 ± 6.0 mg/kg/d. Subjects on alternative treatment (N = 67) initiated hydroxyurea and 60 (90%) reached MTD at 26.2 ± 4.9 mg/kg/d with 29.1% ± 6.7% fetal hemoglobin (HbF). Adjudication documented no strokes on transfusions/chelation but 7 (10%) on hydroxyurea/phlebotomy, still within the noninferiority stroke margin. The National Heart, Lung, and Blood Institute closed SWiTCH after interim analysis revealed equivalent liver iron content, indicating futility for the composite primary end point. Transfusions and chelation remain a better way to manage children with SCA, stroke, and iron overload.

Stroke recurrence in children with sickle cell disease treated with hydroxyurea following first clinical stroke

Chronic transfusion therapy is the treatment of choice for preventing stroke recurrence in children with sickle cell disease (SCD). The majority of children affected by this devastating complication live in the developing world where access to regular blood transfusions may be impractical. Since 2000, in the absence of regular blood supplies, all children at the Sickle Cell Unit who had experienced a first clinical stroke were offered hydroxyurea (HU) as the only intervention to prevent stroke recurrence. Forty-four children were identified as having experienced a first clinical stroke between January 1, 2000 and September 30, 2009; one died at that presentation. Forty-three children were therefore followed for 111 person-years, of whom 10 (23.3%) agreed to start HU. Only one child in the HU group, incidence rate 2/100 person-years, had clinical stroke recurrence, compared to 20/33 in the non-HU group, incidence rate 29/100 person-years (Hazard ratio (HR) 9.4 [95% Confidence interval (CI): 1.3-70.6]; P = 0.03). When the groups were compared, in the non-HU group, four died (vs. zero), 13 (53% vs. 10%) had moderate-severe physical disability (P = 0.017), and 12 (44% vs. 20%) required special education or were too disabled to attend school. Our data support the role of HU as a useful intervention for prevention of stroke recurrence in SCD when transfusion programs are not available or practical.

Clinical and Laboratory Effects of Hydroxyurea in Children and Adolescents with Sickle Cell Anemia: A Portuguese Hospital Study

Our aim was to assess the efficacy and safety of hydroxyurea (HU) in children with severe forms of sickle cell anemia followed in a Portuguese hospital. We carried out an open-label uncontrolled prospective study, which included children with severe forms of sickle cell anemia. Hydroxyurea was started at 15 mg/kg/day and increased to a maximum dose of 25 mg/kg/day. Patients were monitored to assess compliance, clinical and hematological response and toxicity. Nine children and adolescents, five girls and four boys, with a median age of 13 years (range 8 to 16) were enrolled in the study during a period of 24 months. All patients completed at least 15 months of therapy. Hb F was significantly increased, from a mean of 7.0 +/- 3.9% to 13.7 +/- 5.3% (p = 0.028). Clinically, all patients responded significantly with a reduction of 80% in the number of vaso-occlusive crises (VOC), 69% in hospital admissions, 76% in hospitalization days and 67% in transfusion requirements, without significant toxicity. We concluded that, in our population, HU proved to be effective in increasing Hb F levels, and in decreasing hospitalizations for VOC and transfusion requirements with no major side effects. Long-term clinical follow-up is important to certify benefit maintenance.

Sickle cell disease in Africa: burden and research priorities

Sickle cell disease (SCD) has recently been recognised as a problem of major public-health significance by the World Health Organization. Despite the fact that >70% of sufferers live in Africa, expenditure on the related care and research in the continent is negligible, and most advances in the understanding and management of this condition have been based on research conducted in the North. In order to target limited resources, African countries need to focus research and interventions on areas that will lead to the maximum impact. This review details the epidemiological and clinical background of SCD, with an emphasis on Africa, before identifying the research priorities that will provide the necessary evidence base for improving the management of African patients. Malaria, bacterial and viral infections and cerebrovascular accidents are areas in which further research may lead to a significant improvement in SCD-related morbidity and mortality. As patients with high concentrations of foetal haemoglobin (HbF) appear to be protected from all but mild SCD, the various factors and pharmacological agents that might increase HbF levels need to be assessed in Africa, as options for interventions that would improve quality of life and reduce mortality.

Pathophysiology and treatment of stroke in sickle-cell disease: present and future

Sickle-cell anaemia is the most common cause of stroke in children, and stroke is one of the most devastating complications of sickle-cell disease. Overt strokes are typically due to large-artery vasculopathy affecting the intracranial internal carotid arteries and proximal middle cerebral arteries, whereas silent strokes typically occur in the territory of penetrating arteries. The sickled red blood cell can contribute to the pathogenesis of stroke via abnormal adherence to the vascular endothelium and by haemolysis, which results in endothelial cell activation, a hypercoaguable state, and alterations in vasomotor tone. Red-blood-cell transfusion, the most common preventive measure for stroke in sickle-cell disease, is associated with iron overload in chronic disease. Therefore, interventions directed towards the potential mechanisms that promote vasculopathy and occlusion in sickle-cell anaemia should be investigated. Here we review the epidemiology, clinical spectrum, and pathophysiology of stroke in sickle-cell disease to identify potential therapeutic targets.

Advances in the management of sickle cell disease

This article summarizes my presentation at the Pediatric Hematology-Oncology Symposium in honor of Dr. Stephen A. Feig in April 2005. Areas highlighted reflect key topics whose evolution parallel and were impacted by Steve's exceptional academic career. It is by no means an exhaustive summation of all advances in the biology and treatment of sickle cell disease. The interested reader is encouraged to consider a number of well written recently published reviews that cover additional areas of scientific and medical advancement in the pathophysiology and care of sickle cell disease 1-5.

Defining stroke risk in children with sickle cell anaemia

Sickle cell anaemia (SCA) is the most common cause of childhood stroke, occurring with the highest frequency before the age of 6 years. Despite the relative frequency of stroke in SCA, few predictors of risk exist. Anaemia, leucocytosis, hypertension, silent infarction, and history of acute chest syndrome are well-documented risk factors for ischaemic stroke in SCA. Recent data suggest that other environmental and genetic factors, many unrelated to SCA, influence the development of cerebrovascular disease. Non-invasive assessment of individual stroke risk using transcranial Doppler ultrasonography has provided a means of selecting and prophylactically treating SCA children at highest risk. With the ultimate goal of preventing stroke, the information gained from the studies reviewed here may lead to improved prediction of stroke so that clinical trials to assess risk-based therapy may be carried out on selected children with SCA.

Prevention of secondary stroke and resolution of transfusional iron overload in children with sickle cell anemia using hydroxyurea and phlebotomy

OBJECTIVE

Transfusions prevent secondary stroke in children with sickle cell anemia (SCA) but also cause iron overload. Alternatives for stroke prophylaxis with effective therapy to reduce iron burden are needed.

STUDY DESIGN

For 35 children with SCA and stroke, transfusions were prospectively discontinued. Hydroxyurea was prescribed for stroke prophylaxis, and phlebotomy removed excess iron. Initial patients discontinued transfusions before hydroxyurea therapy, but later patients overlapped transfusions with hydroxyurea until tolerating full-dose therapy.

RESULTS

Children received hydroxyurea for 42 +/- 30 months (range, 3-104 months). Hydroxyurea (26.7 +/- 4.8 mg/kg per day) led to mild neutropenia (3.9 +/- 2.3 x 10(9)/L) with significant increases in hemoglobin concentration, mean corpuscular volume, and fetal hemoglobin. Stroke recurrence rate was 5.7 events per 100 patient-years, but children receiving overlapping hydroxyurea therapy had only 3.6 events per 100 patient-years. For 26 children with >6 months of phlebotomy, 14,311 +/- 12,459 mL blood (315 +/- 214 mL/kg) was removed, with serum ferritin decreasing from a median of 2722 to 298 ng/mL. Among patients completing phlebotomy, liver biopsy documented normal histology and no excess iron deposition.

CONCLUSIONS

For children with SCA and stroke, hydroxyurea effectively prevents secondary stroke and serial phlebotomy leads to complete resolution of transfusional iron overload.

Stroke in children with sickle cell anaemia: aetiology and treatment

Cerebral infarction is a frequent, severe complication of sickle cell anaemia. During childhood, most strokes are due to infarction with the majority resulting from occlusion of the large cerebral arteries. Risk factors include transient ischaemic attacks, acute chest syndrome, severe anaemia and elevated blood pressure. Less certain is the association with leucocytosis, or protection provided by alpha-thalassaemia or fetal haemoglobin. Children who have one stroke are at significant risk for having subsequent events that can be substantially reduced by maintaining haemoglobin S below 30%. It has not yet been possible to identify individuals for whom transfusion can be safely stopped. Haemosiderosis is a consequence of intensive and long term transfusion therapy, which requires chelation with deferoxamine. Iron accumulation can be minimised using erythrocytapheresis but this is technically difficult in children, expensive and results in increased donor exposure. In addition to lesions associated with strokes, an additional 17% of patients can be shown to have clinically silent cerebral infarcts. Although these are termed 'silent', those affected have mild neuropsychological deficits. Their relationship to stroke or risk for recurrence is unknown. Transfusion therapy has been shown to provide primary stroke prevention for children who have elevated cerebral artery velocity. Finally, intracranial haemorrhages, more commonly found in adults, also affect children. Subarachnoid haemorrhage is frequently found to result from cerebral artery aneurysms. A condition that mimics the moyamoya syndrome radiographically, as well as for its risk of haemorrhage, can be found in children with partly occluded cerebral arteries either as a result of stroke or silent infarct.

Flow cytometric method for simultaneous assay of foetal haemoglobin containing red cells, reticulocytes and foetal haemoglobin containing reticulocytes

Level of foetal haemoglobin (HbF) containing red cells (F cells) is a parameter for monitoring sickle cell anaemia (SS) patients undergoing treatment with HbF modulating drugs (including hydroxyurea (HU)). One convenient technique for F cell assay is flow cytometry. A flow cytometric method for the simultaneous assay of F cells, reticulocytes and HbF-containing reticulocytes (F reticulocytes) is described in this paper. These three parameters can be obtained within 2 h using double colour staining flow cytometry. Glutaraldehyde fixation, Triton X-100 permeabilization, monoclonal antibody to HbF Tri-colour conjugate (MoAb-HbF-TC; deep-red fluorescence) immuno-staining and thiazole orange (TO; green fluorescence) are employed. The red cell gate was set on forward scatter (FSC) and logarithmic side scatter (logSSC) for 50 000 cells on the flow cytometer. Fluorescent signals were acquired from fluorescent channel 1 (FL1; green) and (FL4; deep-red). Coefficient of variation percent (%CVs) of intra- and inter-assay were less than 9% and 15%, respectively. EDTA, citrate, heparin and CTAD anticoagulants are all suitable; the samples can be stored at 4 degrees C for up to 6 days. The method is a simple, rapid, convenient, reproducible and useful way of determining F cell, reticulocyte and F reticulocyte levels in sickle cell and thalassaemic patients.

Stroke in hemoglobin (SD) sickle cell disease with moyamoya: successful hydroxyurea treatment after cerebrovascular bypass surgery

An 11-year-old boy with hemoglobin sickle disease (HbSD), bilateral stenosis of the intracranial carotid arteries, and moyamoya syndrome had recurrent ischemic strokes with aphasia and right hemiparesis. His parents (Jehovah's Witnesses) refused blood transfusions. After bilateral extracranial-intracranial (EC-IC) bypass surgery, hydroxyurea treatment increased hemoglobin F (HbF) levels to more than 30%. During a follow-up of 28 months, flow velocities in the basal cerebral arteries remained stable, neurologic sequelae regressed, and ischemic events did not recur. This is the first report of successful hydroxyurea treatment after bypass surgery for intracranial cerebral artery obstruction with moyamoya syndrome in sickle cell disease. The patient's religious background contributed to an ethically challenging therapeutic task. (Blood. 2001;97:2165-2167)

Use of hydroxyurea in children ages 2 to 5 years with sickle cell disease

The efficacy and side effects of hydroxyurea in young children with sickle cell disease are unknown. The authors followed-up eight young children (mean age 3.7 years) during therapy with hydroxyurea for an average of 137 weeks. Total and fetal hemoglobin levels rose with hydroxyurea therapy. Hospital admission rates and total hospital days decreased during hydroxyurea therapy. No unexpected toxicity occurred, and growth and development were unaffected. This pilot study suggests that hydroxyurea is safe and effective in young children with sickle cell disease.

New Views of Sickle Cell Disease Pathophysiology and Treatment

This review addresses several areas of concern in the care of patients with sickle cell disease. In Sections I and II, the fundamental pathogenetic mechanisms of sickle cell disease and their clinical consequences are discussed. Dr. Narla presents the evidence for abnormal cell adhesiveness by SS cells and Dr. Rosse examines the role of the increased whole blood viscosity. In Section III, Dr. Petz reviews common and uncommon alloimmune consequences of transfusion in sickle cell disease and discusses the diagnosis and management of sickle cell patients with hyperhemolysis after transfusion. In Section IV, Dr. Steinberg gives an update on the use of hydroxyurea in the treatment of sickle cell disease, including the SC and S-β thalassemia variants.

New Views of Sickle Cell Disease Pathophysiology and Treatment

This review addresses several areas of concern in the care of patients with sickle cell disease. In Sections I and II, the fundamental pathogenetic mechanisms of sickle cell disease and their clinical consequences are discussed. Dr. Narla presents the evidence for abnormal cell adhesiveness by SS cells and Dr. Rosse examines the role of the increased whole blood viscosity. In Section III, Dr. Petz reviews common and uncommon alloimmune consequences of transfusion in sickle cell disease and discusses the diagnosis and management of sickle cell patients with hyperhemolysis after transfusion. In Section IV, Dr. Steinberg gives an update on the use of hydroxyurea in the treatment of sickle cell disease, including the SC and S-β thalassemia variants.

Hydroxyurea as an Alternative to Blood Transfusions for the Prevention of Recurrent Stroke in Children With Sickle Cell Disease

Children with sickle cell disease (SCD) and stroke receive chronic transfusions to prevent stroke recurrence. Transfusion risks including infection, erythrocyte allosensitization, and iron overload suggest a need for alternative therapies. We previously used hydroxyurea (HU) and phlebotomy in two young adults with SCD and stroke as an alternative to transfusions. We have now prospectively discontinued transfusions in 16 pediatric patients with SCD and stroke. Reasons to discontinue transfusions included erythrocyte alloantibodies or autoantibodies, recurrent stroke on transfusions, iron overload, noncompliance, and deferoxamine allergy. HU was started at 15 mg/kg/d and escalated to 30 mg/kg/d based on hematologic toxicity. Patients with iron overload underwent phlebotomy. The children have been off transfusions 22 months, (range, 3 to 52 months). Their average HU dose is 24.9 ± 4.2 mg/kg/d, hemoglobin concentration is 9.4 ± 1.3 g/dL, and mean corpuscular volume (MCV) is 112 ± 9 fL. Maximum percentage fetal hemoglobin (%HbF) is 20.6% ± 8.0% and percentage HbF-containing erythrocytes (%F cells) is 79.3% ± 14.7%. Fourteen patients underwent phlebotomy with an average of 8,993 mL (267 mL/kg) removed. Serum ferritin has decreased from 2,630 to 424 ng/mL, and 4 children have normal ferritin values. Three patients (19%) had neurological events considered recurrent stroke, each 3 to 4 months after discontinuing transfusions, but before maximal HU effects. These preliminary data suggest some children with SCD and stroke may discontinue chronic transfusions and use HU therapy to prevent stroke recurrence. Phlebotomy is well-tolerated and significantly reduces iron overload. Modifications in HU therapy to raise HbF more rapidly might increase protection against stroke recurrence.

Hydroxyurea as an Alternative to Blood Transfusions for the Prevention of Recurrent Stroke in Children With Sickle Cell Disease

Children with sickle cell disease (SCD) and stroke receive chronic transfusions to prevent stroke recurrence. Transfusion risks including infection, erythrocyte allosensitization, and iron overload suggest a need for alternative therapies. We previously used hydroxyurea (HU) and phlebotomy in two young adults with SCD and stroke as an alternative to transfusions. We have now prospectively discontinued transfusions in 16 pediatric patients with SCD and stroke. Reasons to discontinue transfusions included erythrocyte alloantibodies or autoantibodies, recurrent stroke on transfusions, iron overload, noncompliance, and deferoxamine allergy. HU was started at 15 mg/kg/d and escalated to 30 mg/kg/d based on hematologic toxicity. Patients with iron overload underwent phlebotomy. The children have been off transfusions 22 months, (range, 3 to 52 months). Their average HU dose is 24.9 ± 4.2 mg/kg/d, hemoglobin concentration is 9.4 ± 1.3 g/dL, and mean corpuscular volume (MCV) is 112 ± 9 fL. Maximum percentage fetal hemoglobin (%HbF) is 20.6% ± 8.0% and percentage HbF-containing erythrocytes (%F cells) is 79.3% ± 14.7%. Fourteen patients underwent phlebotomy with an average of 8,993 mL (267 mL/kg) removed. Serum ferritin has decreased from 2,630 to 424 ng/mL, and 4 children have normal ferritin values. Three patients (19%) had neurological events considered recurrent stroke, each 3 to 4 months after discontinuing transfusions, but before maximal HU effects. These preliminary data suggest some children with SCD and stroke may discontinue chronic transfusions and use HU therapy to prevent stroke recurrence. Phlebotomy is well-tolerated and significantly reduces iron overload. Modifications in HU therapy to raise HbF more rapidly might increase protection against stroke recurrence.

Erythrocyte autoantibodies in paediatric patients with sickle cell disease receiving transfusion therapy: frequency, characteristics and significance

The formation of erythrocyte autoantibodies following transfusion therapy has been described in case reports and small series. To determine the frequency, serological characteristics, and clinical significance of this phenomenon in paediatric patients with sickle cell disease, we analysed the patient database at the Duke University Pediatric Hematology Clinic. We identified children who received multiple erythrocyte transfusions, then reviewed clinical records to identify children who developed erythrocyte autoantibodies in association with transfusions. Among 184 paediatric patients who received multiple erythrocyte transfusions, 14 children (7.6%) developed warm (IgG) erythrocyte autoantibodies. Median transfusion exposure at the time of autoantibody formation was 24 erythrocyte units, range 3-341 units. The autoantibody reacted as a panagglutinin in 11 cases but had anti-e specificity in three patients. Surface complement also was detected in five patients. Clinically significant haemolysis was documented in four patients, each of whom had both surface IgG and C3 detected. The development of erythrocyte autoantibodies was associated with the presence of erythrocyte alloantibodies. Formation of warm erythrocyte autoantibodies in association with transfusions is not rare in paediatric patients with sickle cell disease. Clinicians should be aware of this complication and recognize that the presence of surface C3 is often associated with significant haemolysis.

The enzyme ribonucleotide reductase: target for antitumor and anti-HIV therapy

Ribonucleotide reductase is the rate-limiting enzyme of DNA synthesis, and it has been shown to be linked with malignant transformation and tumor cell proliferation. It was therefore considered as an excellent target for cancer chemotherapy. This article reviews the in vitro and in vivo effects of hydroxyurea the first inhibitor of the enzyme, which is currently used in general clinical practice. In addition, we summarize the results obtained with other inhibitors of the enzyme; for instance, polyhydroxy-substituted benzohydroxamic acid derivatives, a promising group of inhibitors of ribonucleotide reductase that was synthesized by Bart van'T Riet and investigated by our group. In vitro as well as animal data and pharmacokinetic results are reviewed and possible implications for an improvement in the management of various patient groups are outlined.

Discontinuation of long-term transfusion therapy in patients with sickle cell disease and stroke

Long-term transfusion therapy in patients with sickle cell disease and stroke markedly decreases the risk of stroke recurrence. However, it is not known how long the transfusions should be continued. Published reports have documented a high risk of stroke recurrence after stopping transfusion. We report on nine consecutive patients with sickle cell disease and stroke whose long-term transfusion therapy was discontinued and in whom no ischemic strokes developed during 80.75 patient years of follow-up.

Fetal Hemoglobin in Sickle Cell Anemia: Determinants of Response to Hydroxyurea

Hydroxyurea (HU) can increase fetal hemoglobin (HbF) in sickle cell anemia (HbSS). To identify determinants of the HbF response, we studied 150 HU-treated patients grouped by quartiles of change in HbF from baseline to 2 years. Half of the HU-assigned patients had long-term increments in HbF. In the top two quartiles, HbF increased to 18.1% and 8.8%. These patients had the highest baseline neutrophil and reticulocyte counts, and largest treatment-associated decrements in these counts. In the lower two quartiles, 2-year HbF levels (4.2% and 3.9%) and blood counts changed little from baseline. In the highest HbF response quartile, myelosuppression developed in less than 6 months, compliance was best, and final doses of HU were 15 to 22.5 mg/kg. All four quartiles had substantial increases of F cells in the first year. This was maintained for 2 years only in the top three quartiles. Leukocyte and reticulocyte counts decreased initially in all quartiles, but drifted back toward baseline levels in the lowest HbF response quartile. Initial HbF level and phenotype of the F-cell production (FCP) locus were not associated with HbF response, but absence of a Central African Republic (CAR) haplotype was. Bone marrow ability to withstand HU treatment may be important for sustained HbF increases during HU treatment of HbSS.

Systemic fat embolism and pulmonary hypertension in sickle cell disease

Systemic fat embolism, a relatively rare complication of sickle cell disease, is difficult to diagnose and it is often fatal. A high index of suspicion and early transfusion therapy may provide the best chance for recovery. Sickle cell-related pulmonary hypertension can be documented by cardiac catheterization but has no proven treatment. Patients with this complication are usually adults, have a poor prognosis, and may be considered for hydroxyurea treatment. Administration of vasodilators, anticoagulation, or oxygen may be beneficial in selected individuals.