Risk factors and prediction of outcomes in children and adolescents who have sickle cell anemia

Multi-center study on mortality in children, and adults with sickle cell anemia-risk factors and causes of death

Sickle cell disease (SCD) is a major public health burden worldwide with increasing morbidity and mortality. The study evaluates the risk factors associated with mortality in SCD patients, between the years 2006 and 2020 at three hospitals in Oman. The analysis includes clinical manifestations, haematological, biochemical, and radiological parameters, use of antibiotics, and blood and exchange transfusions. Our cohort included 123 patients (82 males, 41 females), with a median age of 27 (Interquartile Range 21-35 years). SCD related complications included acute chest syndrome (ACS) in 52.8%, splenic sequestration in 21.1%, right upper quadrant syndrome in 19.5%, more than > 6 VOC/year in 17.9%, and stroke in 13.8%. At the terminal admission, patients had cough, reduced O2 saturation, crepitation and fever in 24.4%, 49.6%, 53.6% and 68.3% respectively. Abnormal chest X-ray and chest CT scan were seen in 57.7%, and 76.4% respectively. Laboratory parameters showed a significant drop in hemoglobin (Hb) and platelet counts from baseline, with a significant rise in WBC, LDH and CRP from baseline (p < 0.05, Wilcoxon Signed Ranks test). All patients received antibiotics, whereas, 95.9% and 93.5% received simple blood transfusions, and exchange transfusions respectively, and 66.6% required non-invasive ventilation. Among the causes of death, ACS is seen in 32 (26%), sepsis in 49 (40%), and miscellaneous in 42 (34%). Sudden death was seen in 32 (26%) of patients. Male gender, with low HbF, rapid drop in Hb and platelet, and increased in WBC, LDH, ferritin, and CRP, correlated significantly with mortality in this cohort.

Predicting risk factors for thromboembolic complications in patients with sickle cell anaemia - lessons learned for prophylaxis

Objective

To assess the clinical and laboratory predictors of venous thromboembolism (VTE) in patients with sickle cell anaemia (SCA) and its relationship to morbidity and mortality.

Methods

This retrospective case–control study analysed data from patients with SCA that experienced VTE compared with matched control patients with SCA but no VTE (2:1 ratio).

Results

A total of 102 patients with SCA were enrolled (68 cases with VTE and 34 controls). Amongst the 68 cases (median age, 29.5 years), 26 (38.2%) presented with isolated pulmonary embolism (PE). A higher prevalence of splenectomy (73.5% versus 35.3%) was observed in the cases compared with the controls. A significantly higher prevalence of central venous catheter (CVC) insertion (42.6% versus 8.8%) was observed in the cases compared with the controls. High white blood cell counts, serum lactic dehydrogenase (LDH), bilirubin and C-reactive protein (CRP) and low haemoglobin (Hb) and HbF were significant risk factors for VTE. Forty-two cases (61.8%) developed acute chest syndrome, 10 (14.7%) had a stroke and seven (10.3%) died.

Conclusions

VTE in patients with SCA has a high impact on morbidity and mortality. PE was the leading presentation of VTE, with CVC insertion, high LDH, bilirubin, CRP and white blood cell counts along with low Hb and HbF constituting other significant risk factors.

Current and future gene therapies for hemoglobinopathies

PURPOSE OF REVIEW

In this work we briefly summarize the key features and currently available conventional therapies for the two main β-hemoglobinopathies, sickle cell disease (SCD) and β-thalassemia, and review the rapidly evolving field of novel and emerging genetic therapies to cure the disease.

RECENT FINDINGS

Gene therapy using viral vectors or designer nuclease-based gene editing is a relatively new field of medicine that uses the patient's own genetically modified cells to treat his or her own disease. Multiple different approaches are currently in development, and some have entered phase I clinical studies, including innovative therapies aiming at induction of fetal hemoglobin.

SUMMARY

Early short-term therapeutic benefit has been reported for some of the ongoing clinical trials, but confirmation of long-term safety and efficacy remains to be shown. Future therapies aiming at the targeted correction of specific disease-causing DNA mutations are emerging and will likely enter clinical testing in the near future.

Influence of alpha thalassemia on clinical and laboratory parameters among nigerian children with sickle cell anemia

BACKGROUND

There is paucity of data on the influence of alpha thalassemia on the clinical and laboratory parameters among Nigerian sickle cell anemia (SCA) patients. This study aimed to determine the prevalence of alpha thalassemia and the influence of alpha thalassemia on laboratory parameters and clinical manifestations in a group of young Nigerian SCA patients.

METHODS

This was a cross-sectional retrospective study conducted on 100 patients with SCA and 63 controls. The diagnosis of SCA was confirmed by DNA studies. Alpha thalassemia genotyping was performed by multiplex gap-PCR method. Laboratory parameters including complete blood count, hemoglobin quantitation, serum lactate dehydrogenase (LDH), and bilirubin were determined with standard techniques.

RESULTS

Alpha thalassemia was found in 41 (41.0%) patients compared to 24 (38.1%) controls (P = 0.744), and all were due to the 3.7 κb α-globin gene deletions. Alpha thalassemia was associated with more frequent bone pain crisis, higher hemoglobin concentration, red blood cell count, and HbA₂ level among the patients. On the contrary, patients with alpha thalassemia had lower mean corpuscular volume, mean corpuscular hemoglobin, and white blood cell count (WBC) (P ˂ 0.05). There were 6 (6.0%) patients with leg ulcers, and none of them had alpha thalassemia, P = 0.04.

CONCLUSION

This study confirms that coexistence of alpha thalassemia with SCA significantly influences both the clinical and laboratory manifestations of young Nigerian SCA patients. The coexistence of this genetic modifier is associated with increased bone pain crisis and protects against sickle leg ulcers among the patients.

Minireview: Clinical severity in sickle cell disease: the challenges of definition and prognostication

Sickle cell disease (SCD) is a monogenic, yet highly phenotypically variable disease with multisystem pathology. This manuscript provides an overview of many of the known determinants, modifiers, and correlates of disease severity in SCD. Despite this wealth of data, modeling the variable and multisystem pathology of SCD continues to be difficult. The current status of prediction of specific adverse outcomes and global disease severity in SCD is also reviewed, highlighting recent successes and ongoing challenges.

Minireview: Multiomic candidate biomarkers for clinical manifestations of sickle cell severity: Early steps to precision medicine

In this review, we provide a description of those candidate biomarkers which have been demonstrated by multiple-omics approaches to vary in correlation with specific clinical manifestations of sickle cell severity. We believe that future clinical analyses of severity phenotype will require a multiomic analysis, or an omics stack approach, which includes integrated interactomics. It will also require the analysis of big data sets. These candidate biomarkers, whether they are individual or panels of functionally linked markers, will require future validation in large prospective and retrospective clinical studies. Once validated, the hope is that informative biomarkers will be used for the identification of individuals most likely to experience severe complications, and thereby be applied for the design of patient-specific therapeutic approaches and response to treatment. This would be the beginning of precision medicine for sickle cell disease.

Primary stroke in a woman with sickle cell anemia responsive to hydroxyurea therapy

The most common cause of stroke in children with sickle cell anemia is infarction due to ischemia. In adults, however, stroke is most commonly hemorrhagic in nature. Other causes of stroke in patients with sickle cell disease are very rare. In this short communication, we describe a woman with sickle cell anemia responsive to hydroxyurea (HU) therapy who had primary stroke due to paradoxical embolization caused by a large atrial septal defect. Successful management of the stroke included surgical closure of the defect with trans-esophageal echocardiographic guidance. To the best of our knowledge, this is the first patient with sickle cell anemia and stroke due to congenital heart disease who did not require open heart surgery for successful management.

Headache and migraine in children with sickle cell disease are associated with lower hemoglobin and higher pain event rates but not silent cerebral infarction

OBJECTIVE

To identify risk factors for headache and migraine in children with sickle cell disease and test the hypothesis that either or both are independently associated with silent cerebral infarcts.

STUDY DESIGN

In this cross-sectional study, we evaluated the health history, laboratory values, and brain magnetic resonance imaging findings of participants with sickle cell disease (hemoglobinSS or hemoglobinSβ°-thalassemia) with no history of overt stroke or seizures. Participants characterized headache severity and quality. Migraine was defined by International Headache Society criteria modified for increased sensitivity in children. Neuroradiology and neurology committees adjudicated the presence of silent cerebral infarction by review of magnetic resonance imaging and standardized examination by pediatric neurologists.

RESULTS

The cohort included 872 children (51.1% males), ranging in age from 5 to 15 years (mean age, 9.1 years). Of these children, 317 (36.4%) reported recurrent headaches, and 132 (15.1%) reported migraines. In multivariable logistic regression analyses, both were associated with lower steady-state hemoglobin (P = .01 for headaches; P < .01 for migraines) and higher pain rate (P < .01 for headaches; P < .01 for migraines), defined as the number of admissions requiring opioids in the previous 3 years. The presence of silent cerebral infarction was not associated with recurrent headaches or migraines. Only 1.9% (6 of 317) of children with recurrent headaches received medication for headache prophylaxis.

CONCLUSION

Recurrent headaches and migraines are common and undertreated in children with sickle cell disease. Low hemoglobin levels and high pain rates are associated with recurrent headaches and migraines; whereas, silent cerebral infarction is not.

Phenotypic effect of α-globin gene numbers on Indian sickle β-thalassemia patients

BACKGROUND

Sickle cell β-thalassemia is a compound heterozygous state of β-thalassemia and sickle cell anemia. Patient with these conditions showed mild-to-severe clinical phenotype.

OBJECTIVES

The objective of this study was to evaluate the effects of α-globin gene numbers on the phenotype of sickle cell β-thalassemia patients.

MATERIALS AND METHODS

Seventy-five sickle cell β-thalassemia patients were characterized. Clinical, hematological, and molecular characterization was performed in all subjects. Amplified refectory mutation system-polymerase chain reaction was applied for β-thalassemia mutation study while α-genotyping was conducted by Gap-PCR.

RESULTS

Highest frequency of IVS1-5 (33 out of 75 patients) β-thalassemia genotype was recorded. Twenty-eight patients were reported with α-globin chain deletion while four had α-triplications (Anti α-3.7kb). Sickle β-thalassemia patients with α-chain deletions ameliorate hematological and clinical variables.

CONCLUSIONS

This study indicates that the coexistence of α-globin chain deletions showed mild phenotype instead of absence of α-chain deletions while the patients with triplication of α-genes express severe phenotype.

Patent foramen ovale in patients with sickle cell disease and stroke: case presentations and review of the literature

Although individuals with sickle cell disease (SCD) are at increased risk for stroke, the underlying pathophysiology is incompletely understood. Intracardiac shunting via a patent foramen ovale (PFO) is associated with cryptogenic stroke in individuals without SCD. Recent evidence suggests that PFOs are associated with stroke in children with SCD, although the role of PFOs in adults with stroke and SCD is unknown. Here, we report 2 young adults with SCD, stroke, and PFOs. The first patient had hemoglobin SC and presented with a transient ischemic attack and a subsequent ischemic stroke. There was no evidence of cerebral vascular disease on imaging studies and the PFO was closed. The second patient had hemoglobin SS and two acute ischemic strokes. She had cerebral vascular disease with moyamoya in addition to a peripheral deep venous thrombosis (DVT). Chronic transfusion therapy was recommended, and the DVT was managed with warfarin. The PFO was not closed, and the patients' neurologic symptoms were stabilized. We review the literature on PFOs and stroke in SCD. Our cases and the literature review illustrate the dire need for further research to evaluate PFO as a potential risk factor for stroke in adults with SCD.

Acute silent cerebral ischemia and infarction during acute anemia in children with and without sickle cell disease

We hypothesized that the silent cerebral infarcts (SCI), which affect up to 40% of children with sickle cell disease (SCD), could occur in the setting of acute anemic events. In a prospective observational study of children with and without SCD hospitalized for an illness associated with acute anemia, we identified acute silent cerebral ischemic events (ASCIE) in 4 (18.2%) of 22 with SCD and in 2 (6.7%) of 30 without SCD, using diffusion-weighted magnetic resonance imaging. Children with ASCIE had lower hemoglobin concentration than those without (median 3.1 vs 4.4 g/dL, P = .003). The unique temporal features of stroke on diffusion-weighted magnetic resonance imaging permit estimation of incidence rates for ASCIE of 421 (95% confidence interval, 155-920) per 100 patient-years during acute anemic events for all patients. For children with SCD, the estimated incidence was 663 (95% confidence interval, 182-1707) which is much higher than previously reported. Acute anemic events are common in children with SCD and prevalence could partially account for the high SCI. Some ASCIE (1 of 4 in our study) may be reversible. Alterations in management may be warranted for children with severe anemia to identify unrecognized ischemic brain injury that may have permanent neurocognitive sequelae.

Prevalence of intracardiac shunting in children with sickle cell disease and stroke

OBJECTIVE

To determine the prevalence of potential intracardiac shunts, including patent foramen ovale (PFO), in children with sickle cell disease (SCD) and stroke.

STUDY DESIGN

We performed a transthoracic echocardiogram (TTE) on 40 children with SCD (39 with hemoglobin SS and 1 with sickle-beta0 thalassemia) and earlier stroke (overt stroke in 30, silent infarction in 10). We compared 3 TTE techniques: conventional 2-dimensional imaging, color Doppler ultrasound, and intravenous agitated saline contrast injection for the detection of intracardiac shunts. We also evaluated the clinical, laboratory, and radiographic findings of the children with and without shunts.

RESULTS

We identified PFO or other potential intracardiac shunts in 10 of 40 children with SCD and earlier stroke (25%; 95% CI, 11.6-38.4). With contrasted TTE, we failed to detect potential shunts in 2 children. In a comparison group of 60 children with stroke but without SCD, retrospective review of clinical echocardiograms identified PFO in 7 of 60 (11.7%; 95% CI, 3.6-19.8). Clinical features significantly associated with the presence of intracardiac shunts were stroke in the setting of vaso-occlusive crisis (P = .026) and headache at stroke onset (P = .014).

CONCLUSION

One-quarter of children with SCD and stroke have potential intracardiac shunts. A combination of echocardiographic techniques is required for optimal shunt detection. Intracardiac shunting could be a risk factor for stroke in children with SCD because they are predisposed to thrombosis and elevations of right heart pressure, which could promote paradoxical embolization across an intracardiac shunt.

Acute silent cerebral infarction in children with sickle cell anemia

Silent cerebral infarctions (SCI) occur in up to 35% of children with sickle cell anemia (HbSS) but are rarely recognized during the initial 10-14 days when diffusion weighted magnetic resonance imaging (MRI) can differentiate acute infarctions from remote events. We report acute SCI in seven children with HbSS who had areas of restricted diffusion on MRI without persistent focal neurologic deficits. Four had acute SCI identified following acute anemic events. Our observations suggest that SCI are detectible in the acute phase, present with subtle neurologic symptoms, result in permanent neurologic injury, and may be caused by acute anemic events.

Stroke in sickle cell anemia: alternative etiologies

Stroke is common in children with sickle cell anemia, but is rarely attributed to the traditional causes of stroke identified in other children. An 11-year-old girl with sickle cell anemia presented with severe headache and was found to have recurrent bilateral multifocal strokes in a cardioembolic pattern. Evaluation revealed the presence of a patent foramen ovale, antiphospholipid antibodies, and elevations in factor VIII and lipoprotein(a). Sickle cell anemia is itself a hypercoagulable state with potential for increased right heart pressures, both of which predispose to paradoxical embolization via right-to-left intracardiac shunting of emboli, thus causing stroke. The present case suggests that the more traditional etiologies for pediatric stroke may also cause stroke in children with sickle cell anemia.

Monocyte protein signatures of disease severity in sickle cell anemia

Using two-dimensional difference gel electrophoresis (2D DIGE) we have analyzed monocytes derived from 10 sickle cell disease patients (5 males and 5 females ages 12-18) to generate hypotheses regarding signature proteins that appear most positively and negatively correlated with vasoocclusive event rate. Signature proteins have been identified by tandem mass spectrometry. Based on the limited number of samples analyzed, the most negatively correlated proteins related to crises rate were transketolase and coronin in the membrane fraction and heat shock 70 kDa protein cognate 4, and adenylate kinase isoenzyme 2, mitochondrial found in the cytosolic fraction. The protein spots that were most positively correlated with crisis rate in the cytoplasmic fraction were far upstream element-binding protein and Alpha actinin 1 or Alpha actinin 4. Utilizing StepSIM analysis, vinculin was able to classify all samples from the combined set and the membrane-only set, and cytosolic leukotriene A-4 hydrolase and phosphoglycerate kinase were also identified as important indicators for differentiating between low and high vasoocclusive event rates.

Lung function and somatic growth in patients with hemoglobin SC sickle cell disease

OBJECTIVE

To investigate the changes in lung function and somatic growth that occur over time in children with hemoglobin SC (Hb-SC) sickle cell disease (SCD).

METHODS

Measurements of lung function and somatic growth were performed in patients with Hb-SC twice with an interval of 50.2 +/- 26.0 months. Comparisons were made with a group of patients with hemoglobin SS (Hb-SS) SCD, matched by age, race, and gender who underwent similar testing and served as controls.

RESULTS

Indices of lung function in patients with Hb-SC were and remained within the normal range in the two testing periods and they were significantly higher than those measured among patients with Hb-SS. However, there was significant and similar decline (as percentage from baseline) over time in both groups (forced vital capacity, FVC: -3.7 +/- 9.4 vs. -3.8 +/- 14.2; forced expiratory volume in the first second, FEV1: -7.4 +/- 9.3 vs. -6.8 +/- 15.2; forced expiratory flow at 25-75% of FVC, FEF(25-75): -13.7 +/- 20.6 vs. -12.1 +/- 24.7 for Hb-SC and Hb-SS respectively). The body mass index (BMI, percentile) was significantly (P < 0.05) higher among patients with Hb-SC (49 +/- 36 vs. 26 +/- 18) and increased over time in both groups (50 +/- 33 vs. 32 +/- 31).

CONCLUSION

Lung function is generally normal among children with Hb-SC, but it declines over time in a fashion similar to that observed among patients with Hb-SS SCD. The decline is slow and it is not associated with changes in somatic growth. Our findings suggest that patients with Hb-SC should probably have the same close follow-up as patients with Hb-SS.

Daytime steady-state haemoglobin desaturation is a risk factor for overt stroke in children with sickle cell anaemia

Haemoglobin (Hb) desaturation could increase the risk of stroke in sickle cell anaemia (SS) by perturbing endothelial function and limiting oxygen delivery to the brain. We performed a nested case-control study of the Dallas Newborn Cohort to determine whether daytime steady-state Hb desaturation was associated with overt stroke in children with SS. Cases had SS and overt ischaemic strokes. Controls had comparable genotypes but no overt stroke. Cases had lower prestroke steady-state pulse oximetry values (SpO(2)) than controls, and cases' SpO(2) fell even lower as the time to impending stroke decreased. The odds ratio for stroke was 1.32 for each 1% decrease in SpO(2). In conclusion, steady-state Hb desaturation is a risk factor for overt ischaemic stroke in children with SS. Decline in SpO(2) over time further increases this risk. Hb desaturation is easily measured, potentially modifiable, and could be used to identify children with SS at increased risk of stroke.

Prediction of adverse outcomes in children with sickle cell anemia: a study of the Dallas Newborn Cohort

The Cooperative Study of Sickle Cell Disease reported that dactylitis, severe anemia, and leukocytosis in very young children with sickle cell disease (SCD) increased the risk of later adverse outcomes, including death, stroke, frequent pain, and recurrent acute chest syndrome. This model has not been validated in other cohorts. We evaluated its performance in the Dallas Newborn Cohort, a newborn inception cohort of children with SCD. We studied 168 children (55% male, 97% sickle cell anemia) with a mean follow-up of 7.1 years who provided 1188 patient-years of observation. Of the 23 (13.7%) subjects who experienced adverse events, 2 (1.2%) died, 14 (8.3%) had a stroke, 4 (2.4%) had frequent pain, and 3 (1.8%) had recurrent acute chest syndrome. No relationship existed between early clinical predictors and later adverse outcomes, with the possible exception of leukocyte count. Most subjects who experienced adverse events were predicted to be at low risk for those events. No subject who was predicted to be at high risk actually experienced an adverse outcome. The sensitivity of the model did not rise above 20% until specificity fell below 60%. We suggest that this model not be used as a criterion to initiate early interventions for SCD.

Has stem cell transplantation come of age in the treatment of sickle cell disease?

Currently, hematopoietic SCT (HCT) is the only intervention that can restore normal hematopoiesis to provide a 'cure' in sickle cell disease. Yet, this treatment modality is used sparsely-a total of less than 400 transplants are reported in the Center for International Blood and Marrow Transplant Research database despite 70,000 afflicted in the United States; 88% of transplants are from HLA-matched sibling donors and 84% are <16 years of age at transplant. Overall survival at 3 years is over 90% after HCT in the young but 62% in adult HCT recipients due to increased disease and transplant-related morbidity. The decision and timing of HCT is a dilemma for physicians and families due to the need to consider HCT before severe organ damage in a disease that is generally not fatal in children with adequate supportive care. From the transplant physician's perspective, however, advances in the ability to identify well-matched donors, supportive care and promising conditioning regimens with low toxicity and transplant complications support the development of new HCT trials for sickle cell disease as the risk/benefit ratio can be balanced better. With the recognition of new predictors of early mortality, the anticipation of extensive and expensive life-long medical support, and the poor quality of life despite medical care, the scales tip in favor of HCT. This is prime time for the development of careful unrelated donor HCT trials for sickle cell disease. Research efforts targeting HCT will need to be directed at seeking safe and effective transplant methods applicable to all patients who might derive benefit.

Deconstructing sickle cell disease: reappraisal of the role of hemolysis in the development of clinical subphenotypes

Hemolysis, long discounted as a critical measure of sickle cell disease severity when compared with sickle vaso-occlusion, may be the proximate cause of some disease complications. New mechanistic information about hemolysis and its effects on nitric oxide (NO) biology and further examination of the subphenotypes of disease requires a reappraisal and deconstruction of the clinical features of sickle cell disease. The biology underlying clinical phenotypes linked to hemolysis may increase our understanding of the pathogenesis of other chronic hemolytic diseases while providing new insights into treating sickle cell disease. The pathophysiological roles of dysregulated NO homeostasis and sickle reticulocyte adherence have linked hemolysis and hemolytic rate to sickle vasculopathy. Nitric oxide binds soluble guanylate cyclase which converts GTP to cGMP, relaxing vascular smooth muscle and causing vasodilatation. When plasma hemoglobin liberated from intravascularly hemolyzed sickle erythrocytes consumes NO, the normal balance of vasoconstriction:vasodilation is skewed toward vasoconstriction. Pulmonary hypertension, priapism, leg ulceration and stroke, all subphenotypes of sickle cell disease, can be linked to the intensity of hemolysis. Hemolysis plays less of a role in the vaso-occlusive-viscosity complications of disease like the acute painful episode, osteonecrosis of bone and the acute chest syndrome. Agents that decrease hemolysis or restore NO bioavailability or responsiveness may have potential to reduce the incidence and severity of the hemolytic subphenotypes of sickle cell disease. Some of these drugs are now being studied in clinical trials.

Prognostic significance of early vaso-occlusive complications in children with sickle cell anemia

Sickle cell anemia (SS) is highly phenotypically variable, and early predictors of outcome could guide clinical care. To determine whether early vaso-occlusive complications predicted subsequent adverse outcomes in the Dallas Newborn Cohort, we studied all members with SS or sickle-beta0-thalassemia who presented in their first year of life and had 5 years or more of follow-up. We defined 3 potential early predictors: hospitalizations in the first 3 years of life for (1) painful events other than dactylitis, (2) dactylitis, and (3) acute chest syndrome (ACS). We studied the associations of these predictors with the following late adverse outcomes (occurring after the third birthday): death, first overt stroke, use of disease-modifying therapy, and hospitalizations for pain events and ACS. None of the early events predicted death or stroke. Early pain and ACS both predicted a modest, temporary increase in the number of later painful episodes, but early ACS strongly increased the odds of more frequent ACS throughout childhood. Dactylitis had limited utility as a predictor. Although we still lack a useful prognostic framework for young children with SS, those who experience early ACS might be candidates for higher risk interventions to mitigate or cure their disease.

Promoting children's health through understanding of genetics and genomics

PURPOSE

To describe the effects of genetics and genomics on children's health care.

ORGANIZING CONSTRUCT

The breakthroughs in the Human Genome Project have great potential for disease prediction, treatment, and prevention in the health care of children with chronic health conditions. Most childhood conditions based on a single gene are influenced by a complex interaction of genetic and environmental factors.

METHODS

A review of the literature was conducted to determine the most common childhood diseases linked to genetic causes.

FINDINGS

Two examples were selected to depict how a health professional would use genetic knowledge to provide holistic health promotion and disease prevention.

CONCLUSIONS

Knowledge of the interaction of the genetic profile coupled with a person's lifestyle, work environment, and family context provide a more holistic picture of a person's health profile. The clinical implications are that this knowledge will provide opportunities for health professionals to advise families on individualized treatment options or to tailor health promotion to future disease states based on genes and their interaction with the environment.

Sickle Cell Disease

Much progress has been made during the past several decades in gaining understanding about the natural history of sickle cell disease and management approaches aimed at treating or even preventing certain disease complications. The characterization of the human genome now offers the opportunity to understand relationships regarding how gene polymorphisms as well as how environmental factors affect the sickle cell disease phenotype, i.e., the individual patient’s overall clinical severity as well as their specific organ function. This chapter explores some of these recent advances in knowledge.

In Section I, Dr. Michael DeBaun characterizes the problem of silent stroke in sickle cell disease, comparing and contrasting its clinical and neuroimaging features with overt stroke. Combined, these events affect virtually 40% of children with sickle cell anemia. New understanding of risk factors, associated clinical findings, and imaging technologies are impacting substantially on treatment options. The appreciable cognitive dysfunction and other sequelae of silent infarct demand more effective treatments and ultimate prevention.

In Section II, Dr. Charles Quinn addresses the conundrum of why some patients with sickle cell disease do well whereas others fare poorly. Some risk factors have been known for years, based upon careful study of hundreds of patients by the Cooperative Study for Sickle Cell Disease and investigators studying the Jamaican newborn cohort. Other prognostic measures have only recently been defined. Dr. Quinn devotes special attention to stroke and chest syndrome as organ-related complications but also describes attempts to measure overall disease severity and to predict survival. Recently, investigators have attempted to predict factors responsible for early mortality in children and following onset of pulmonary hypertension in adults.

In Section III, Dr. Martin Steinberg reviews pharmacologic approaches to sickle cell disease and the rationale for their use. In addition to the inhibition of hemoglobin S polymerization, newer targets have been defined during the past one to two decades. These include the erythrocyte membrane, changes in the red cell intracellular content (especially loss of water), endothelial injury, and free radical production. Hydroxyurea treatment attracted the greatest interest, but many uncertainties remain about its long-term benefits and toxicities. Newer “anti-sickling” agents such as decitabine and short-chain fatty acids also receive attention. Prevention of red cell dehydration, “anti-endothelial” therapy, and marshaling the potentially beneficial effects of nitric oxide are other new and exciting approaches.