Asthma and sickle cell disease: two distinct diseases or part of the same process?

Exploring the Interplay between Asthma and Hemoglobinopathies: A Comprehensive Review

Asthma, a prevalent chronic respiratory condition characterized by inflammation of the airways and bronchoconstriction, has demonstrated a potential association with hemoglobinopathies such as thalassemia and sickle cell disease (SCD). Numerous studies have highlighted a higher prevalence of asthma among thalassemia patients compared to the general population, with rates ranging around 30%. Similarly, asthma frequently coexists with SCD, affecting approximately 20-48% of patients. Children with SCD often experience heightened lower airway obstruction and airway hyper-reactivity. Notably, the presence of asthma in SCD exacerbates respiratory symptoms and increases the risk of severe complications like acute chest syndrome, stroke, vaso-occlusive episodes, and early mortality. Several studies have noted a decrease in various cytokines such as IFN-γ and IL-10, along with higher levels of both IL-6 and IL-8, suggesting an overactivation of pro-inflammatory mechanisms in patients with hemoglobinopathies, which could trigger inflammatory conditions such as asthma. The exact mechanisms driving this association are better elucidated but may involve factors such as chronic inflammation, oxidative stress, and immune dysregulation associated with thalassemia-related complications like chronic hemolytic anemia and iron overload. This review aims to comprehensively analyze the relationship between asthma and hemoglobinopathies, with a focus on thalassemia and SCD. It emphasizes the importance of interdisciplinary collaboration among pulmonologists, hematologists, and other healthcare professionals to effectively manage this complex interplay. Understanding this link is crucial for improving care and outcomes in affected individuals.

The influence of body mass index on airway resistance in children with sickle cell disease: A longitudinal study based on impulse oscillometry

BACKGROUND

Impulse oscillometry (IOS) is an effective tool for assessing airway mechanics and diagnosing obstructive airway disease (OAD) in children with sickle cell disease (C-SCD). Obesity is known to be associated with OAD, and untreated OAD often leads to hypoxia-related complications in C-SCD. Considering the increasing prevalence of obesity in C-SCD, it is important to explore the influence of body mass index (BMI) on OAD in this disease population.

METHODS

A longitudinal retrospective chart review was conducted on 55 C-SCD (161 IOS observations) and 35 non-SCD asthmatic children (C-Asthma) (58 observations), primarily to investigate the association between BMI and airway resistance in C-SCD and C-Asthma. We conducted generalized linear mixed models (GLMM), adjusted for pharmacotherapies, to demonstrate the influence of BMI on total (R5), central (R20), and peripheral (R5-20) airway resistance and reactance (X5, resonant frequency (Fres)). We further compared age, BMI, and IOS indices between C-SCD and C-Asthma using the Mann-Whitney test.

RESULTS

Age and BMI were not statistically different between the two groups. In C-SCD, BMI was associated with R5 (GLMM t-statistics:3.75, 95%CI:1.01,3.27, p-value<0.001*) and R20 (t-statistics:4.01, 95%CI:1.04,1.15, p-value<0.001*), but not with R5-20 or airway reactance. In asthmatics, BMI was not associated with IOS estimates except Fres (t-statistics: 3.93, 95%CI: -0.06, -0.02, p-value<0.001*). C-SCD demonstrated higher airway resistances (R5 and R20) and reactance (Fres) compared to C-Asthma (Mann-Whitney: p-values<0.05).

CONCLUSION

BMI significantly influenced total and central airway resistance in C-SCD. While higher airway resistances reflected increased OAD in C-SCD than asthmatics, higher Fres perhaps indicated progressive pulmonary involvement in C-SCD.

Risk factors for acute chest syndrome among children with sickle cell anemia hospitalized for vaso-occlusive crises

Sickle cell anemia (SCA) is a globally prevalent inherited condition, with acute chest syndrome (ACS) being one of its most severe complications. ACS frequently leads to hospitalization, requires intensive care unit (ICU) admission, and can even result in death. This study aimed to discern the early indicators of impending ACS in children with SCA who were initially hospitalized due to painful vaso-occlusive crises (VOC). This was a retrospective, case‒control investigation of 120 patients aged 1-14 years seen at the King Saud Medical City in Riyadh, Saudi Arabia from January 2021 to December 2022. Patients were classified into cases and controls: those who developed and did not develop ACS during hospital stay, respectively. Demographic factors, laboratory results, vital and clinical signs, and treatment protocols were compared between these groups. The following were significant predictors of impending ACS: previous diagnosis of asthma, history of ACS, recent upper respiratory tract symptoms prior to admission, and need for a blood transfusion within the first 24 h of admission due to a drop in hemoglobin levels. Further regression analysis indicated that elevated steady-state mean corpuscular volume, leukocyte count, total bilirubin, and an increased absolute neutrophil count level 24 h after admission also foreshadowed impending ACS among patients admitted for VOC. The location of pain was also significant; the incidence of ACS was higher in patients with back pain, but lower in those with pain confined to the limbs. The ACS group had a longer average duration of hospital stay compared to those with VOC alone, (7.6 vs. 5.8 days). Among patients initially admitted for VOC, 15.7% were diagnosed with ACS. Most ACS cases were managed with transfusions and antibiotics, and nearly one-third of patients needed admission to an ICU or a high-dependency area.

[Lung manifestations of sickle-cell disease]

Sickle-cell disease is an autosomal recessive genetic disorder of hemoglobin that causes systemic damage. Hypoxia is the main actor of sickle-cell disease. It initiates acutely the pathogenic cascade leading to tissue damages that in turn induce chronic hypoxia. Lung lesions represent the major risk of morbidity and mortality. Management of sickle-cell disease requires a tight collaboration between hematologists, intensivists and chest physicians. Recurrent episodes of thrombosis and hemolysis characterize the disease. New therapeutic protocols, associating hydroxyurea, transfusion program and stem cell transplantation in severe cases allow a prolonged survival until the fifth decade. However, recurrent pain, crisis, frequent hospital admissions due to infection, anemia or acute chest syndrome and chronic complications leading to organ deficiencies degrade the patients' quality of life. In low-income countries where the majority of sickle-cell patients are living, the disease is still associated with a high mortality in childhood. This paper focuses on acute chest syndrome and chronic lung manifestations.

Adverse childhood experiences in children and adolescents with sickle cell disease: A retrospective cohort study

BACKGROUND

Adverse childhood experiences (ACEs) are linked to poor health outcomes; however, the relationship between ACEs and health outcomes among children and adolescents with sickle cell disease (SCD) has limited documentation in the published literature.

PROCEDURE

This retrospective cohort study involved 45 children and 30 adolescents. Participants were screened using the Center for Youth Wellness ACE Questionnaire. Parents completed the questionnaire for children. Adolescents provided self-report. ACEs were treated as continuous and categorical scales: 0-1 verus ≥2 original ACEs (individual and/or familial level); 0-1 versus ≥2 additional ACEs (community level); and 0-3 versus ≥4 expanded ACEs (original + additional). Pain and acute chest syndrome events were compared using Wilcoxon rank-sum tests, and correlated with cumulative ACE scores using Spearman's correlation. Multivariable models were fitted to examine the association between ACEs and pain/acute chest syndrome.

RESULTS

The cumulative number of original ACEs positively correlated with acute chest syndrome events (rho = .53, p = .003) and pain (rho = .40, p = .028) among adolescents. Adolescents with ≥2 versus 0-1 original ACEs had a higher number of acute chest syndrome events (4.9 ± 2.6 vs. 1.6 ± 2.2, p = .002); however, this association was confounded by asthma. Acute chest syndrome events and hospitalizations for pain did not differ among child ACE groups. Emergency department (ED) pain visits were higher among children with ≥4 versus 0-3 expanded ACEs (1.6 ± 2.8 vs. 3.3 ± 3.2, p = .042), even after controlling for SCD genotype, asthma, disease-modifying treatment, and follow-up years (p = .027).

CONCLUSION

ACEs are linked to increased morbidity among children and adolescents with SCD. Prospective studies are needed to further understand this relationship and test ACE-protective remedies.

End points for sickle cell disease clinical trials: renal and cardiopulmonary, cure, and low-resource settings

To address the global burden of sickle cell disease and the need for novel therapies, the American Society of Hematology partnered with the US Food and Drug Administration to engage the work of 7 panels of clinicians, investigators, and patients to develop consensus recommendations for clinical trial end points. The panels conducted their work through literature reviews, assessment of available evidence, and expert judgment focusing on end points related to patient-reported outcome, pain (non-patient-reported outcomes), the brain, end-organ considerations, biomarkers, measurement of cure, and low-resource settings. This article presents the findings and recommendations of the end-organ considerations, measurement of cure, and low-resource settings panels as well as relevant findings and recommendations from the biomarkers panel.

How I Treat Acute Chest Syndrome in Asthmatic Children with Sickle Cell Disease. A Practical Review

Asthma is associated with increased rate of acute chest syndrome (ACS), pain episodes and premature death. Differentiating between an acute asthma exacerbation and ACS is a challenge clinically as they can present with similar symptoms. Clinicians should be aware of symptoms of asthma or broncho spasm in any children with sickle cell disease, as adequate treatments are required. In this mini-review, we selected 16 clinical studies, published in English between 2004 and 2016, and reviewed all of the abstracts and references of the selected articles. We subsequently selected articles that were focused on asthma in children with sickle cell disease. Given the pathophysiological mechanisms of ACS and the association between asthma and sickle cell disease, the management approach of asthmatic children should be clarified. Bronchodilators should be used if there are clinical features suggestive of a history of asthma or evidence of acute broncho spasm. The indication for cortisone should be reassessed. This literature review failed to conclude on therapeutic modalities of ACS in asthmatic children with sickle cell disease. Only a well designed, multicenter adequately-powered randomized controlled study of each of them will allow assessing their real benefits and risks.

Asthma, allergic sensitization and lung function in sickle cell disease

BACKGROUND

Pulmonary disease is a frequent acute and chronic manifestation in sickle cell disease (SCD), presenting high morbidity and mortality.

OBJECTIVES

To identify the prevalence and association of asthma, allergic sensitization and altered pulmonary function in patients with SCD (SS and Sβ^o).

METHODS

A single-center, cross-sectional study was conducted, in which 70 patients with SCD and 44 controls, aged six to 18 years, responded to the questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC), complemented with an anamnesis regarding the associated clinical outcomes. All patients underwent immediate hypersensitivity skin tests with aeroallergens and a pulmonary function evaluation (spirometry). Regarding the statistical analysis, parametric and non-parametric methods were used, depending on the variables studied. Tests were considered significant when p<0.05.

RESULTS

There was no significant difference between the patients and controls regarding the prevalence of asthma and allergic sensitization (p>0.05). The number of occurrences of acute chest syndrome per patient per year was significantly higher for asthmatic patients than for non-asthmatic patients (p=0.04). Obstructive pulmonary function occurred in 30.9% of the patients and in 5.4% of the controls, and restrictive pulmonary function occurred in 5.5% of the patients and 5.4% of the controls. Asthma and wheezing in the last 12months had significant associations with obstructive pulmonary function (p=0.014 and p=0.027, respectively).

CONCLUSIONS

The occurrence of asthma, allergic sensitization and alteration in lung function in patients with SCD reinforces the importance of routine monitoring of these diagnoses, which allows for early treatment and prevention of the evolution of pulmonary disease in adulthood.

Pulmonary disease burden in Hispanic and non-Hispanic children with sickle cell disease

RATIONALE

Pulmonary complications are the leading cause of morbidity and mortality in sickle cell disease (SCD) patients. Research in SCD has predominantly been conducted on African-Americans, and the disease burden of SCD in other races and ethnicities, including Hispanic patients, is not well characterized.

OBJECTIVE

To compare pulmonary disease burden between Hispanic and non-Hispanic ethnic groups among children with SCD.

METHODS

In a retrospective chart review on 566 SCD patients followed at the Children's Hospital at Montefiore, NY, we compared the pulmonary disease burden and disease management in Hispanic patients to their non-Hispanic counterparts. We also compared the contribution of demographic and clinical variables to acute chest syndrome (ACS), vaso-occlusive crisis (VOC), and hospitalizations for SCD related complications between the two ethnic groups.

RESULTS

Hispanic patients had a greater proportion of ACS, and had lower forced expiratory volume (FEV1), forced vital capacity, and vital capacity, compared to non-Hispanics. Hispanic patients were more likely to be evaluated in pulmonary clinic and to be on inhaled corticosteroids, short-acting β agonizts, and leukotriene receptor antagonists. In addition, Hispanic children were more likely to be on hydroxyurea, and receive exchange transfusions. However, the association of asthma with the proportion of ACS did not differ between Hispanics and non-Hispanics.

CONCLUSION

Hispanic children with SCD had differences in their pulmonary function profile and received more pulmonary evaluations than non-Hispanic children.

Phase 2 trial of montelukast for prevention of pain in sickle cell disease

Cysteinyl leukotrienes (CysLTs) are lipid mediators of inflammation. In patients with sickle cell disease (SCD), levels of CysLTs are increased compared with controls and associated with a higher rate of hospitalization for pain. We tested the hypothesis that administration of the CysLT receptor antagonist montelukast would improve SCD-related comorbidities, including pain, in adolescents and adults with SCD. In a phase 2 randomized trial, we administered montelukast or placebo for 8 weeks. The primary outcome measure was a >30% reduction in soluble vascular cell adhesion molecule 1 (sVCAM), a marker of vascular injury. Secondary outcome measures were reduction in daily pain, improvement in pulmonary function, and improvement in microvascular blood flow, as measured by laser Doppler velocimetry. Forty-two participants with SCD were randomized to receive montelukast or placebo for 8 weeks. We found no difference between the montelukast and placebo groups with regard to the levels of sVCAM, reported pain, pulmonary function, or microvascular blood flow. Although montelukast is an effective treatment for asthma, we did not find benefit for SCD-related outcomes. This clinical trial was registered at www.clinicaltrials.gov as #NCT01960413.

Airway Inflammation and Lung Function in Sickle Cell Disease

Rationale: Asthma is a common comorbid condition in sickle cell disease (SCD). However, obstructive lung disease is prevalent in SCD, independent of a diagnosis of asthma. It is speculated that the heightened state of inflammation in SCD, involving pathways distinct from allergic asthma, may underlie the SCD-specific obstructive disease. Objective: The objective of the study was to compare airway and systemic inflammatory markers between SCD patients with pulmonary manifestations and patients with allergic asthma, and correlate the discriminating inflammatory markers with clinical measures of pulmonary disease. Materials and Methods: In a pilot translational study conducted at the Children's Hospital at Montefiore, 15 patients with SCD, and history of asthma, airway obstruction, or airway hyper-reactivity, and 15 control patients with allergic asthma 6-21 years of age were recruited. Inflammatory markers, including peripheral blood T helper cell subsets, serum and exhaled breath condensate (EBC) cytokines and chemokines of the Th-1/Th-17, Th-2, and monocytic pathways, and serum cysteinyl leukotrienes B4 (LTB4), were quantified, compared between the study groups, and correlated with atopic sensitization, pulmonary function tests, and markers of hemolysis. Results: White blood cells (P < 0.05) and monocytes (P < 0.001) were elevated in the SCD group, while atopic characteristics were higher in the control asthma group. Tumor necrosis factor-alpha (P < 0.01), interferon gamma inducible protein (IP)-10 (P < 0.05), and interleukin-4 (P < 0.01) in serum and monocyte chemotactic protein (MCP)-1 in EBC were higher in the SCD group (P ≤ 0.05). Forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) in patients with SCD inversely correlated with serum IP-10 and LTB4 levels. Conclusions: Compared with atopic asthmatic patients, inflammatory markers involving Th-1, Th-2, and monocytic pathways were higher in the SCD group, among which Th-1 measures correlated with pulmonary function deficits.

House Dust Mite-Induced Allergic Lung Inflammation Is Not Exacerbated in Sickle Cell Disease Mice

AIM

Asthma appears to be a common comorbid condition in children with sickle cell disease (SCD), and such individuals may be at a higher risk for increased morbidity and mortality. However, several reports have indicated that asthma severity is not particularly high in those with SCD, and airway hyperreactivity and wheeze may be independently associated with SCD. In SCD mice, exacerbated allergic airway disease (AAD) has been observed in response to the model antigen ovalbumin (OVA). We sought to determine if allergic lung inflammation is also exacerbated in SCD mice when they are exposed to the human allergen, house dust mite (HDM).

METHODS AND RESULTS

Eosinophil counts in bronchoalveolar lavage fluid were determined by cytocentrifugation and increased in both wild-type (WT) and SCD mice after acute exposure to a high dose (25 µg) of HDM, which then decreased in chronically exposed mice. WT mice exposed to a low dose of HDM (1 µg) followed the same pattern of eosinophil flux, but SCD mice did not induce much eosinophilia after acute exposure to HDM. As was observed in previous studies, lung lesions similarly increased in severity in both WT and SCD mice after acute exposure to HDM, which remained elevated after chronic exposure. Furthermore, serum HDM-specific IgE titers similarly increased and selected serum cytokines were similar in both WT and SCD mice.

CONCLUSION

These results contrast with previous reports of exacerbated AAD in SCD mice exposed to OVA and support the alternative hypothesis that asthmatic responses are normal in those with SCD.

Sickle Cell Disease: Monitoring, Current Treatment, and Therapeutics Under Development

Screening and early detection of organ injury, as well as expanded use of red cell transfusion and hydroxyurea in children have changed best practices for clinical care in sickle cell disease. The current standard of care for children with sickle cell disease is discussed through a review of screening recommendations, disease monitoring, and approach to treatment. Novel pharmacologic agents under investigation in clinical trials are also reviewed.

How I treat hypoxia in adults with hemoglobinopathies and hemolytic disorders

Hemoglobinopathies are caused by genetic mutations that result in abnormal hemoglobin molecules, resulting in hemolytic anemia. Chronic complications involving the lung parenchyma, vasculature, and cardiac function in hemoglobinopathies result in impaired gas exchange, resulting in tissue hypoxia. Hypoxia is defined as the deficiency in the amount of oxygen reaching the tissues of the body and is prevalent in patients with hemoglobinopathies, and its cause is often multifactorial. Chronic hypoxia in hemoglobinopathies is often a sign of disease severity and is associated with increased morbidity and mortality. Therefore, a thorough understanding of the pathophysiology of hypoxia in these disease processes is important in order to appropriately treat the underlying cause and prevent complications. In this article, we discuss management of hypoxia based on three different cases: sickle cell disease, β-thalassemia, and hereditary spherocytosis. These cases are used to review the current understanding of the disease pathophysiology, demonstrate the importance of a thorough clinical history and physical examination, explore diagnostic pathways, and review the current management.

Identification of therapeutic targets for inflammation in sickle cell disease (SCD) among Indian patients using gene expression data analysis

Sickle cell disease (SCD) is life-threatening hemoglobinopathy prevalent in India, Sub-Saharan Africa and Middle East. Inflammation plays a pivotal role in disease process and involves intricate interaction among leukocytes, platelets, sickle erythrocytes and vascular endothelium. Available disease modifying therapies are hydroxyl-urea and blood transfusion. Therefore, it is of interest to develop improved pharmacological agents for SCD. We report up-regulated genes in steady state and vaso-occlusive crisis using analysis of gene expression data obtained by microarray experiment for SCD as potential targets. The association of these targets with inflammation in pathway analysis is also documented.

Airway inflammation in sickle cell disease-A translational perspective

Asthma and sickle cell disease (SCD) are common chronic conditions in children of African ancestry that are characterized by cough, wheeze, and obstructive patterns on pulmonary function. Pulmonary function testing in children with SCD has estimated a prevalence of obstructive lung disease ranging from 13% to 57%, and airway hyper-responsiveness of up to 77%, independent of a diagnosis of asthma. Asthma co-existing with SCD is associated with increased risk of acute chest syndrome (ACS), respiratory symptoms, pain episodes, and death. However, there are inherent differences in the pathophysiology of SCD and asthma. While classic allergic asthma in the general population is associated with a T-helper 2 cell (Th-2 cells) pattern of cell inflammation, increased IgE levels and often positive allergy testing, inflammation in SCD is associated with different inflammatory pathways, involving neutrophilic and monocytic pathways, which have been explored to a limited extent in mouse models and with a dearth of human studies. The current review summarizes the existent literature on sickle cell related airway inflammation and its cross roads with allergic asthma-related inflammation, and discusses the importance of further elucidating and understanding these common and divergent inflammatory pathways in human studies to facilitate development of targeted therapy for children with SCD and pulmonary morbidity.

Higher prevalence of wheezing and lower FEV1 and FVC percent predicted in adults with sickle cell anaemia: A cross-sectional study

BACKGROUND AND OBJECTIVE

Respiratory symptoms including wheezing are common in adults with sickle cell anaemia (SCA), even in the absence of asthma. However, the prevalence of spirometry changes and respiratory symptoms in adults with SCA is unknown.

METHODS

Using a cross-sectional study design, we tested the hypothesis that adults with SCA (cases) would have higher rates of lower airway obstruction and wheezing than those without SCA (controls) using the American Thoracic Society Division of Lung Diseases' questionnaire. Patients were adults with SCA aged between 18 and 65 years. Controls were consecutive unselected individuals without SCA who presented to an outpatient general medicine clinic.

RESULTS

We enrolled 150 adults with SCA and 287 consecutive controls without SCA. The median age was 23.0 and 27.0 years for adults with and without SCA, respectively. Cases were more likely to report cough without a cold (35.0% vs 18.6%, P < 0.001), lower forced expiratory volume in 1 s (FEV₁ ) % predicted (70.1% vs 82.1%, P = 0.001) and lower forced vital capacity (FVC) % predicted (67.4% vs 74.9%, P = 0.001) than controls. In the multivariable model, wheezing was significantly associated with SCA status (OR = 1.69, 95% CI = 1.08-2.65, P = 0.024). Similarly, FEV₁ % predicted was significantly associated with SCA status and wheezing (P = 0.001 for both).

CONCLUSION

Adults with SCA experience a higher rate of wheezing and impaired respiratory functions compared with controls from the same region.

Asthma as a disruption in iron homeostasis

Over several decades, asthma has evolved from being recognized as a single disease to include a diverse group of phenotypes with dissimilar natural histories, pathophysiologies, responses to treatment, and distinctive molecular pathways. With the application of Occam's razor to asthma, it is proposed that there is one cause underlying the numerous phenotypes of this disease and that the responsible molecular pathway is a deficiency of iron in the lung tissues. This deficiency can be either absolute (e.g. asthma in the neonate and during both pregnancy and menstruation) or functional (e.g. asthma associated with infections, smoking, and obesity). Comparable associations between asthma co-morbidity (e.g. eczema, urticaria, restless leg syndrome, and pulmonary hypertension) with iron deficiency support such a shared mechanistic pathway. Therapies directed at asthma demonstrate a capacity to impact iron homeostasis, further strengthening the relationship. Finally, pathophysiologic events producing asthma, including inflammation, increases in Th2 cells, and muscle contraction, can correlate with iron availability. Recognition of a potential association between asthma and an absolute and/or functional iron deficiency suggests specific therapeutic interventions including inhaled iron.

Inflammatory targets of therapy in sickle cell disease

Sickle cell disease (SCD) is a monogenic globin disorder characterized by the production of a structurally abnormal hemoglobin (Hb) variant Hb S, which causes severe hemolytic anemia, episodic painful vaso-occlusion, and ultimately end-organ damage. The primary disease pathophysiology is intracellular Hb S polymerization and consequent sickling of erythrocytes. It has become evident for more than several decades that a more complex disease process contributes to the myriad of clinical complications seen in patients with SCD with inflammation playing a central role. Drugs targeting specific inflammatory pathways therefore offer an attractive therapeutic strategy to ameliorate many of the clinical events in SCD. In addition, they are useful tools to dissect the molecular and cellular mechanisms that promote individual clinical events and for developing improved therapeutics to address more challenging clinical dilemmas such as refractoriness to opioids or hyperalgesia. Here, we discuss the prospect of targeting multiple inflammatory pathways implicated in the pathogenesis of SCD with a focus on new therapeutics, striving to link the actions of the anti-inflammatory agents to a defined pathobiology, and specific clinical manifestations of SCD. We also review the anti-inflammatory attributes and the cognate inflammatory targets of hydroxyurea, the only Food and Drug Administration-approved drug for SCD.

Risk Factors for Attention and Behavioral Issues in Pediatric Sickle Cell Disease

BACKGROUND

Children with sickle cell disease have an increased risk of neurodevelopmental disorders such as attention deficit hyperactivity disorder, intellectual disability, and specific learning disabilities. Little research has been done to characterize the sickle cell disease-related characteristics associated with neurodevelopmental disorders in the sickle cell disease population.

METHODS

This study was a retrospective chart review involving the outpatient records of 2 medical centers, Kennedy Krieger Institute and Johns Hopkins Hospital. Participants in the study included 59 children with sickle cell disease with a documented neurodevelopmental diagnosis, specifically attention deficit hyperactivity disorder, attention issues, behavioral issues, executive dysfunction, specific learning disabilities in math, reading, and reading comprehension, intellectual disabilities, developmental delay, fine motor disorders, language disorders, or autism spectrum disorders.

RESULTS

Children with sickle cell disease type hemoglobin S-β thalassemia plus had significantly higher odds of attention issues than children with sickle cell disease type hemoglobin SS (OR = 17.0, 95% CI = 1.99-145.00, P < .02). Children with sickle cell disease and a reported history of asthma had significantly higher odds of behavioral issues than children with sickle cell disease without a history of asthma, after adjustment for gender and sickle cell disease type (exact OR = 19.53, 95% CI = 1.16-1369.72, P < .04).

CONCLUSION

Children with sickle cell disease may have increased risk for certain neurodevelopmental diagnoses based on their disease characteristics and associated comorbidities. These preliminary study results should be explored in a larger database.

The Association of Cytokine Levels With Cognitive Function in Children With Sickle Cell Disease and Normal MRI Studies of the Brain

Children with sickle cell disease, including those without evidence for cerebral infarcts, are at increased risk for cognitive deficits that can contribute to difficulties in academic and social functioning. Chronic inflammatory processes are endemic to sickle cell disease and are apparent in common comorbidities including asthma. Cytokines mediating inflammatory processes can influence cognition. The authors examined the relationship between plasma levels of cytokines commonly associated with asthma and cognitive functioning using standardized neuropsychological measures in 25 children with sickle cell disease with normal magnetic resonance imaging studies of the brain. Children with sickle cell disease performed significantly below the normative mean on tests of cognitive function. Pearson correlations indicated significant negative relations between cytokines (IL-4, IL-5, IL-8, and IL-13) and standardized tests of executive function (r = -.54 to -.74). Preliminary evidence suggests an association between cytokine levels and executive function in children with sickle cell disease, indicating a potential role for inflammatory processes in cognitive outcomes in these children.

Increased risk of severe vaso-occlusive episodes after initial acute chest syndrome in children with sickle cell anemia less than 4 years old: Sleep and asthma cohort

Previous studies have shown that the highest incidence of acute chest syndrome (ACS) in sickle cell disease occurs in children <4 years old, and a history of ACS at this age is a risk factor for future ACS episodes. However, the interval associated with the highest risk of subsequent ACS or severe pain is not known. Through this mixed retrospective-prospective observational study, the Sleep and Asthma Cohort, we sought to determine the interval after an initial ACS episode during which the majority of children <4 years old are rehospitalized for ACS or severe pain. The cumulative prevalence of rehospitalization for ACS or severe pain within 6 months, 1 years, and 2 years was calculated for children with an initial ACS episode <4 years old and compared to children with an initial ACS episode ≥4 years old. A total of 44.8% and 55.2% of participants had an initial ACS episode <4 years and ≥4 years old (Range: 4-17.7 years), respectively. At 1 year following the initial ACS episode, children <4 years old had a significantly higher cumulative prevalence of rehospitalizations for ACS or pain as compared to children ≥4 years of age, 62.5 and 39.1%, respectively (P = 0.009). After initial ACS episodes, the majority of children <4 years old will be rehospitalized for ACS or severe pain within one year, suggesting the need for a therapeutic intervention for this high-risk group.

Sickle erythrocytes and platelets augment lung leukotriene synthesis with downregulation of anti-inflammatory proteins: relevance in the pathology of the acute chest syndrome

Initiation, progression, and resolution of vaso-occlusive pain episodes in sickle cell disease (SCD) have been recognized as reperfusion injury, which provokes an inflammatory response in the pulmonary circulation. Some 5-lipoxygenase (5-lox) metabolites are potent vasoconstrictors in the pulmonary circulation. We studied stimulation of production of the inflammatory eicosanoids leukotrienes (LTs) and prostaglandin E2 (PGE2) by isolated rat lungs perfused with sickle (HbSS) erythrocytes. Our hypothesis is that HbSS erythrocytes produce more LTs than normal (HbAA) erythrocytes, which can induce vaso-occlusive episodes in SCD patients. Lung perfusates were collected at specific time points and purified by high-pressure liquid chromatography, and LTC4 and PGE2 contents were measured by enzyme-linked immunosorbent assay (ELISA). Rat lung explants were also cultured with purified HbAA and HbSS peptides, and 5-lox, cyclooxygenase 1/2, and platelet-activating factor receptor (PAFR) proteins were measured by Western blotting, while prostacyclin and LTs produced by cultured lung explants were measured by ELISA. Lung weight gain and blood gas data were not different among the groups. HbSS-perfused lungs produced more LTC4 and PGE2 than HbAA-perfused lungs: 10.40 ± 0.62 versus 0.92 ± 0.2 ng/g dry lung weight (mean ± SEM; P = 0.0001) for LTC4. Inclusion of autologous platelets (platelet-rich plasma) elevated LTC4 production to 12.6 ± 0.96 and 7 ± 0.60 ng/g dry lung weight in HbSS and HbAA perfusates, respectively. HbSS lungs also expressed more 5-lox and PAFR. The data suggest that HbSS erythrocytes and activated platelets in patient's pulmonary microcirculation will enhance the synthesis and release of the proinflammatory mediators LTC4 and PGE2, both of which may contribute to onset of the acute chest syndrome in SCD.

Genome-wide association studies in Africans and African Americans: expanding the framework of the genomics of human traits and disease

Genomic research is one of the tools for elucidating the pathogenesis of diseases of global health relevance and paving the research dimension to clinical and public health translation. Recent advances in genomic research and technologies have increased our understanding of human diseases, genes associated with these disorders, and the relevant mechanisms. Genome-wide association studies (GWAS) have proliferated since the first studies were published several years ago and have become an important tool in helping researchers comprehend human variation and the role genetic variants play in disease. However, the need to expand the diversity of populations in GWAS has become increasingly apparent as new knowledge is gained about genetic variation. Inclusion of diverse populations in genomic studies is critical to a more complete understanding of human variation and elucidation of the underpinnings of complex diseases. In this review, we summarize the available data on GWAS in recent African ancestry populations within the western hemisphere (i.e. African Americans and peoples of the Caribbean) and continental African populations. Furthermore, we highlight ways in which genomic studies in populations of recent African ancestry have led to advances in the areas of malaria, HIV, prostate cancer, and other diseases. Finally, we discuss the advantages of conducting GWAS in recent African ancestry populations in the context of addressing existing and emerging global health conditions.

Factors predicting future ACS episodes in children with sickle cell anemia

While a doctor-diagnosis of asthma is associated with an increased risk of pain and acute chest syndrome (ACS) in children with sickle cell anemia (SCA), little is known about the relationship between specific asthma characteristics and clinical factors and future morbidity in children with SCA. We evaluated the relationship between (i) asthma risk factors at the time of a clinical visit (respiratory symptoms, maternal history of asthma, allergy skin tests, spirometry results) and (ii) the known risk factor of ACS early in life, on prospective pain and ACS episodes in a cohort of 159 children with SCA followed from birth to a median of 14.7 years. An ACS episode prior to 4 years of age, (incidence rate ratio [IRR] = 2.84; P < 0.001], female gender (IRR = 1.80; P = 0.009), and wheezing causing shortness of breath (IRR = 1.68; P = 0.042) were associated with future ACS rates. We subsequently added spirometry results (obstruction defined as FEV1 /FVC less than the lower limits of normal; and bronchodilator response, FEV1 ≥ 12%) and prick skin test responses to the model. Only ≥ 2 positive skin tests had a significant effect (IRR 1.87; P = 0.01). Thus, early in life ACS events, wheezing causing shortness of breath, and ≥ 2 positive skin tests predict future ACS events.

Randomization is not associated with socio-economic and demographic factors in a multi-center clinical trial of children with sickle cell anemia

BACKGROUND

Few studies have investigated factors influencing participation rates for minority children with a chronic disease in clinical trials. The Silent Cerebral Infarct Multi-Center Clinical (SIT) Trial provides an opportunity to study the impact of demographic and socio-economic factors on randomization in a clinical trial among Black children. Our primary objective was to characterize the factors associated with successful randomization of children with sickle cell disease (SCD) and silent cerebral infarct (SCI) in the SIT Trial after initial consent.

PROCEDURE

Differences in socio-economic and demographic variables, family history and disease-related variables were determined between eligible participants who were successfully randomized and those who were not randomized following initial consent. Head of household educational level and family income were examined separately for US versus non-US sites.

RESULTS

Of 1,176 children enrolled in the SIT Trial, 1,016 (86%) completed screening. Of 208 (20%) children with qualifying SCI on pre-randomization MRI, 196 (94%) were successfully randomized. There were no differences in socio-economic, demographic, or disease-related variables between children who were or were not randomized. Participants from non-US sites were more likely to be randomized (22% vs. 12%, P = 0.011); although, randomization by country was associated with neither head of household education nor family income.

CONCLUSION

In the SIT Trial, acceptance of random allocation was not associated with socio-economic or demographic factors. Although these factors may represent barriers for some participants, they should not bias investigators caring for children with SCD in their approach to recruitment for clinical trial participation.

Progression and prognostic indicators of bronchial disease in children with sickle cell disease

PURPOSE

The pulmonary complications of sickle cell disease (SCD) are a leading cause of morbidity and mortality (MacLean et al. Am J Respir Crit Care Med 178:1055-1059, 2008; Klings et al. Am J Respir Crit Care Med 173:1264-1269, 2006; National Heart, Lung, and Blood Institute, 2009). Despite this recognition, predictive markers of lung dysfunction progression remain elusive (Klings et al. Am J Respir Crit Care Med 173:1264-1269, 2006; Platt et al. N Engl J Med 330:1639-1644, 1994; Caboot et al. Curr Opin Pediatr 20:279-287, 2008; Field et al. Am J Hematol 83:574-576, 2008; Shirlo et al. Peadiatr Respir Review 12:78-82, 2011). This study was designed describe the longitudinal progression and identify specific markers that influence bronchial disease in SCD.

METHODS

A retrospective, chart review of 89 patients with SCD was conducted. All patients underwent spirometry in conjunction with body plethysmography as part of routine care. Eleven lung function variables were assessed, five of which were selected to establish patterns of normal, obstructive, restrictive, or mixed obstructive-restrictive physiology (Klings et al. Am J Respir Crit Care Med 173:1264-1269, 2006; Field et al. Am J Hematol 83:574-576, 2008).

RESULTS

In the unadjusted model, forced expiratory volume in one second (FEV1)% of predicted trended downward with age, while total lung capacity (TLC)% of predicted showed a bimodal distribution and carbon monoxide diffusion capacity corrected for hemoglobin (DLCOcor)% of predicted remained stable. Adjusting for acute chest syndrome (ACS) episodes, medication status, and growth velocity (GV), the final model demonstrated that the downward trend between FEV1% of predicted with age was further influenced by the latter two factors.

CONCLUSIONS

Initial decline in FEV1% of predicted is associated with worsening pulmonary dysfunction over time. Independent of ACS episodes, the factors most influential on the progression of FEV1% predicted include the introduction of medications as well as the promotion of adequate prepubertal growth. Efforts to ensure normal prepubertal GV and treatment with bronchodilators, such as short-acting beta(2) agonists and inhaled corticosteroids (ICS), should be considered at an early age to delay progression of pulmonary dysfunction.

Differences in the clinical and genotypic presentation of sickle cell disease around the world

Sickle cell disease (SCD), caused by a mutation in the β-globin gene HBB, is widely distributed in malaria endemic regions. Cardiopulmonary complications are major causes of morbidity and mortality. Hemoglobin SS (Hb SS) represents a large proportion of SCD in the Americas, United Kingdom, and certain regions of Africa while higher proportions of hemoglobin SC are observed in Burkina Faso and hemoglobin Sβ-thalassemia in Greece and India. Coinheritance of α-thalassemia and persistence of hemoglobin F production are observed in highest frequency in certain regions of India and the Middle East. As confirmed in the PUSH and Walk-PHaSST studies, Hb SS, absence of co-inheriting alpha-thalassemia, and low hemoglobin F levels tend to be associated with more hemolysis, lower hemoglobin oxygen saturations, greater proportions of elevated tricuspid regurgitant jet velocity and brain natriuretic peptide, and increased left ventricular mass index. Identification of additional genetic modifiers will improve prediction of cardiopulmonary complications in SCD.

Wheezing in children with sickle cell disease

PURPOSE OF REVIEW

The purpose of this article is to provide a comprehensive review of wheezing in sickle cell disease (SCD), including epidemiology, pathophysiology, associations between wheezing and SCD morbidity and finally the clinical approach to evaluation and management of individuals with SCD who wheeze.

RECENT FINDINGS

Wheezing is common in SCD and in some individuals represents an intrinsic component of SCD-related lung disease rather than asthma. Emerging data suggest that, regardless of the cause, individuals with SCD and with recurrent wheezing are at increased risk for subsequent morbidity and premature mortality. We believe individuals who acutely wheeze and have respiratory symptoms should be managed with a beta agonist and short-term treatment of oral steroids, typically less than 3 days to attenuate rebound vaso-occlusive disease. For those who wheeze and have a history or examination associated with atopy, we consider asthma treatment and monitoring per National Heart, Lung and Blood Institute asthma guidelines.

SUMMARY

Wheezing in SCD should be treated aggressively both in the acute setting and with controller medications. Prospective SCD-specific clinical trials will be necessary to address whether anti-inflammatory asthma therapies (leukotriene antagonists, inhaled corticosteroids) can safely mitigate the sequelae of wheezing in SCD.

Sickle cell disease in childhood: from newborn screening through transition to adult medical care

Sickle cell disease (SCD) is the name for a group of related blood disorders caused by an abnormal hemoglobin molecule that polymerizes on deoxygenation. SCD affects the entire body, and the multisystem pathophysiology begins in infancy. Thanks to prognostic and therapeutic advancements, some forms of SCD-related morbidity are decreasing, such as overt stroke. Almost all children born with SCD in developed nations now live to adulthood, and lifelong multidisciplinary care is necessary. This article provides a broad overview of SCD in childhood, from newborn screening through transition to adult medical care.

Pulmonary function abnormalities and asthma are prevalent in children with sickle cell disease and are associated with acute chest syndrome

Pulmonary diseases form major sources of morbidity and mortality in children with sickle cell disease (SCD). The objective of the study was to determine the prevalence of lung function abnormalities and asthma and their association with acute chest syndrome (ACS) in children with SCD. This was a cross-sectional retrospective study of 127 children with SCD; we collected information regarding ACS and asthma and pulmonary function test (PFT) data. Based on PFT results, the patients were assigned to one pattern of lung function [normal, obstructive lung disease (OLD), restrictive lung disease (RLD)]. Statistical analyses included Pearson correlation, prevalence odds ratio (POR), cross-tabulation, and multiple binary logistic regression. OLD was noted in 35% and RLD in 23% of the patients, with the remainder exhibiting a normal PFT pattern. Forty-six percent of patients had asthma, 64% of whom had a history of ACS. OLD (r = .244, P = .008, POR = 2.8) and asthma (r = .395, P < .001, POR = 5.4) were significantly associated with a history of ACS. There was a negative correlation between having normal PFT data and a history of ACS (r = -.289, P = .002, POR = .3). Asthma and pulmonary function abnormalities are prevalent in children with SCD, with OLD being more common than RLD. There is an association between asthma, OLD, and ACS, however causality cannot be proven due to the study design. We stress the importance of actively investigating for a clinical diagnosis of asthma in all patients with SCD and suggest that PFT data may help detect patients at lower risk for ACS.

Biomedical research, a tool to address the health issues that affect African populations

Traditionally, biomedical research endeavors in low to middle resources countries have focused on communicable diseases. However, data collected over the past 20 years by the World Health Organization (WHO) show a significant increase in the number of people suffering from non-communicable diseases (e.g. heart disease, diabetes, cancer and pulmonary diseases). Within the coming years, WHO predicts significant decreases in communicable diseases while non-communicable diseases are expected to double in low and middle income countries in sub-Saharan Africa. The predicted increase in the non-communicable diseases population could be economically burdensome for the basic healthcare infrastructure of countries that lack resources to address this emerging disease burden. Biomedical research could stimulate development of healthcare and biomedical infrastructure. If this development is sustainable, it provides an opportunity to alleviate the burden of both communicable and non-communicable diseases through diagnosis, prevention and treatment. In this paper, we discuss how research using biomedical technology, especially genomics, has produced data that enhances the understanding and treatment of both communicable and non-communicable diseases in sub-Saharan Africa. We further discuss how scientific development can provide opportunities to pursue research areas responsive to the African populations. We limit our discussion to biomedical research in the areas of genomics due to its substantial impact on the scientific community in recent years however, we also recognize that targeted investments in other scientific disciplines could also foster further development in African countries.

Sickle-Cell Trait and Atopic and Inflammatory Disease in Children

Roughly 9% of African-Americans carry 1 copy of the sickle β-globin allele [sickle-cell trait (SCT)]. The sickle allele may affect the host responses in a way that protects against sequelae of malaria. Besides the association with sporadic episodes of erythrocyte sickling, acute chest syndrome, and sudden death, the SCT is generally regarded as asymptomatic. Separately, and for unclear reasons, the African-Americans have an elevated risk compared to whites for several immune-mediated diseases, including asthma, eczema, and other respiratory conditions. We propose to determine whether the SCT contributes to the elevated risk of these inflammatory conditions. We performed a retrospective cohort study of children with and without the sickle trait to assess the risk for common immune-mediated conditions. The cohorts were individually matched, and multiple logistic regression was used with variables selected using a backward stepwise approach. A second approach (case-control design) assessed the odds of the SCT among African-Americans with and without asthma. We found 2,481 children with and 4,962 matched patients without the SCT in the cohort design. The sickle trait was associated with greater odds for several immune-mediated conditions in a multivariable analysis, but not associated with asthma (odds ratio, OR=1.10, P=0.212). In an adjusted case-control analysis (n=20,000), the sickle trait was weakly associated with asthma [adjusted odds ratio (aOR)=1.46, 1.01-2.13]. In both the designs and in all statistical models used, we found that the SCT was associated with bronchitis (aOR=1.71, 1.09-2.67) and eczema (aOR=1.74, 1.23-2.46). The SCT may contribute to an increased risk for eczema and asthma-like symptoms in the African-American children.

Considerations for Care: Management of Asthma in the Child with Sickle Cell Disease

Asthma is difficult to diagnose in the child with sickle cell disease because symptoms and pulmonary function abnormalities are similar to the spectrum of pulmonary manifestations in sickle cell disease. There are no published reports of controlled trials of asthma medications in children with sickle cell disease. Thus, treatment decisions should be guided by the Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma (www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf). However, issues specific to children with sickle cell disease should be considered. Initial strategies should focus on control of environmental triggers, as effectiveness on asthma outcomes is proven and the cost for implementation can be low. Use of short- and long-acting β₂-agonists may prolong QTc, particularly in this population of children who already have a higher prevalence of prolonged QTc than the general population. Long-acting β₂-agonist use has been associated with life-threatening asthma exacerbations with potentially higher risks in African Americans. Montelukast has been reported to increase suicidal thinking and behavior, and persons with asthma and sickle cell disease are already at risk for these events. Oral corticosteroids in the treatment of acute chest syndrome may increase risk of readmission even in children with asthma. The lack of prospective controlled trials of asthma drug treatment in children with asthma and sickle cell disease compels us to move this issue forward.

Wheezing and asthma are independent risk factors for increased sickle cell disease morbidity

To assess the associations between a doctor diagnosis of asthma and wheezing (independent of a diagnosis of asthma) with sickle cell disease (SCD) morbidity, we conducted a retrospective review of Emergency Department (ED) visits to the Mount Sinai Medical Center for SCD between 1 January 2007 and 1 January 2011. Outcomes were ED visits for pain and acute chest syndrome. The cohort included 262 individuals, median age 23·8 years, (range: 6 months to 67·5 years). At least one episode of wheezing recorded on a physical examination was present in 18·7% (49 of 262). Asthma and wheezing did not overlap completely, 53·1% of patients with wheezing did not carry a diagnosis of asthma. Wheezing was associated with a 118% increase in ED visits for pain (95% confidence interval [CI]: 56-205%) and a 158% increase in ED visits for acute chest syndrome (95% CI: 11-498%). A diagnosis of asthma was associated with a 44% increase in ED utilization for pain (95% CI: 2-104%) and no increase in ED utilization for acute chest syndrome (rate ratio 1·00, 95%CI 0·41-2·47). In conclusion, asthma and wheezing are independent risk factors for increased painful episodes in individuals with SCD. Only wheezing was associated with more acute chest syndrome.

Risk factors for increased ED utilization in a multinational cohort of children with sickle cell disease

OBJECTIVES

The objective was to identify clinical, social, and environmental risk factors for increased emergency department (ED) use in children with sickle cell disease (SCD).

METHODS

This study was a secondary analysis of ED utilization data from the international multicenter Silent Cerebral Infarct Transfusion (SIT) trial. Between December 2004 and June 2010, baseline demographic, clinical, and laboratory data were collected from children with SCD participating in the trial. The primary outcome was the frequency of ED visits for pain. A secondary outcome was the frequency of ED visits for acute chest syndrome.

RESULTS

The sample included 985 children from the United States, Canada, England, and France, for a total of 2,955 patient-years of data. There were 0.74 ED visits for pain per patient-year. A past medical history of asthma was associated with an increased risk of ED utilization for both pain (rate ratio [RR] = 1.28, 95% confidence interval [CI] = 1.04 to 1.58) and acute chest syndrome (RR = 1.60, 95% CI = 1.03 to 2.49). Exposure to environmental tobacco smoke in the home was associated with 73% more ED visits for acute chest syndrome (RR = 1.73, 95% CI = 1.09 to 2.74). Each $10,000 increase in household income was associated with 5% fewer ED visits for pain (RR = 0.95, 95% CI = 0.91 to 1.00, p = 0.05). The association between low income and ED utilization was not significantly different in the United States versus countries with universal health care (p = 0.51).

CONCLUSIONS

Asthma and exposure to environmental tobacco smoke are potentially modifiable risk factors for greater ED use in children with SCD. Low income is associated with greater ED use for SCD pain in countries with and without universal health care.

Pulmonary complications of sickle cell disease

Sickle cell disease (SCD) is a common monogenetic disorder with high associated morbidity and mortality. The pulmonary complications of SCD are of particular importance, as acute chest syndrome and pulmonary hypertension have the highest associated mortality rates within this population. This article reviews the pathophysiology, diagnosis, and treatment of clinically significant pulmonary manifestations of SCD, including acute chest syndrome, asthma, and pulmonary hypertension in adult and pediatric patients. Clinicians should be vigilant in screening and treating such comorbidities to improve patient outcomes.

Outpatient follow-up and rehospitalizations for sickle cell disease patients

BACKGROUND

Rehospitalization rates are increasingly used as quality indicators for a variety of illnesses, including sickle cell disease. While one small, single center study suggested outpatient follow-up with a pediatric hematologist was associated with fewer rehospitalizations, no study has examined the effect of post-discharge outpatient follow-up on rehospitalization rates across ages and beyond a single site.

PROCEDURE

This is a retrospective cohort study using Wisconsin Medicaid claims data for hospitalized children and adults with sickle cell disease from 2003 to 2007. The primary outcomes were rehospitalization at both 14 and 30 days after an index hospitalization for sickle cell pain crisis (ICD-9-CM codes 28242, 28262, 28264, 28269). Univariate survival analyses were performed based on outpatient visit, severe disease, asthma, and age. The Cox proportional hazards model was used for multivariate analyses yielding hazard ratios for the association between outpatient visits and subsequent rehospitalization rates.

RESULTS

Of the 408 patients included, 42 (10.2%) patients were rehospitalized within 14 days and 70 (17.1%) were rehospitalized within 30 days. Multivariate analysis showed that an outpatient visit is associated with lower rates of both 30-day rehospitalization (Hazard Ratio (HR) 0.442; 95%CI: 0.330-0.593) and 14-day rehospitalization (HR 0.226; 95%CI: 0.124-0.412), with the majority of 30-day rehospitalizations occurring within 14 days.

CONCLUSIONS

For sickle cell disease, post-discharge planning should emphasize early follow-up to prevent subsequent hospitalization and improve care quality. Pediatr Blood Cancer 2012; 58: 406-409. © 2011 Wiley Periodicals, Inc.

Markers of severe vaso-occlusive painful episode frequency in children and adolescents with sickle cell anemia

OBJECTIVE

To identify factors associated with frequent severe vaso-occlusive pain crises in a contemporary pediatric cohort of patients with sickle cell anemia (SCA) enrolled in a prospective study of pulmonary hypertension and the hypoxic response in sickle cell disease.

STUDY DESIGN

Clinical and laboratory characteristics of children with SCA who had ≥3 severe pain crises requiring health care in the preceding year were compared with those of subjects with <3 such episodes.

RESULTS

Seventy-five children (20%) reported ≥3 severe pain episodes in the preceding year, and 232 (61%) had none. Frequent pain episodes were associated with older age (OR, 1.2; 95% CI, 1.1-1.3; P < .0001), α-thalassemia trait (OR 3.5; 1.6-6.7; P = .002), higher median hemoglobin (OR 1.7; 95% CI: 1.2-2.4; P < .003), and lower lactate dehydrogenase concentration (OR 1.82; 95% CI: 1.07-3.11; P = .027). Children with high pain frequency also had an increased iron burden (serum ferritin, 480 vs 198 μg/L; P = .006) and higher median tricuspid regurgitation jet velocity (2.41 vs 2.31 m/s; P = .001). Neither hydroxyurea use nor fetal hemoglobin levels were significantly different according to severe pain history.

CONCLUSIONS

In our cohort of children with SCA, increasing age was associated with higher frequency of severe pain episodes as were α-thalassemia, iron overload, higher hemoglobin and lower lactate dehydrogenase concentration, and higher tricuspid regurgitation velocity.

Asthma morbidity and treatment in children with sickle cell disease

Children with sickle cell disease (SCD) and a comorbid condition of asthma have increased numbers of vaso-occlusive pain and acute chest syndrome episodes, and all-cause mortality. When assessed systematically, asthma prevalence is probably similar among children with SCD when compared with the general African-American population. With increasing recognition of the importance of asthma in the management of SCD, hematologists must become familiar with asthma and develop a multidisciplinary approach, including early recognition, appropriate management and referral to asthma specialists.

Sickle cell disease: the need for a public health agenda

Sickle cell disease (SCD) is a collection of inherited blood disorders that affect a substantial number of people in the U.S., particularly African Americans. People with SCD have an abnormal type of hemoglobin, Hb S, which polymerizes when deoxygenated, causing the red blood cells to become misshapen and rigid. Individuals with SCD are at higher risk of morbidity and mortality from infections, vaso-occlusive pain crises, acute chest syndrome, and other complications. Addressing the public health needs related to SCD is an important step toward improving outcomes and maintaining health for those affected by the disorder. The objective of this study was to review public health activities focusing on SCD and define the need to address it more comprehensively from a public health perspective. We found that there has been some progress in the development of SCD-related public health activities. Such activities include establishing newborn screening (NBS) for SCD with all states currently having universal NBS programs. However, additional areas needing focus include strengthening surveillance and monitoring of disease occurrence and health outcomes, enhancing adherence to health maintenance guidelines, increasing knowledge and awareness among those affected, and improving healthcare access and utilization. These and other activities discussed in this paper can help strengthen public health efforts to address SCD.

Arginase and arginine dysregulation in asthma

In recent years, evidence has accumulated indicating that the enzyme arginase, which converts L-arginine into L-ornithine and urea, plays a key role in the pathogenesis of pulmonary disorders such as asthma through dysregulation of L-arginine metabolism and modulation of nitric oxide (NO) homeostasis. Allergic asthma is characterized by airway hyperresponsiveness, inflammation, and remodeling. Through substrate competition, arginase decreases bioavailability of L-arginine for nitric oxide synthase (NOS), thereby limiting NO production with subsequent effects on airway tone and inflammation. By decreasing L-arginine bioavailability, arginase may also contribute to the uncoupling of NOS and the formation of the proinflammatory oxidant peroxynitrite in the airways. Finally, arginase may play a role in the development of chronic airway remodeling through formation of L-ornithine with downstream production of polyamines and L-proline, which are involved in processes of cellular proliferation and collagen deposition. Further research on modulation of arginase activity and L-arginine bioavailability may reveal promising novel therapeutic strategies for asthma.

Asthma in sickle cell disease: implications for treatment

Objective. To review issues related to asthma in sickle cell disease and management strategies. Data Source. A systematic review of pertinent original research publications, reviews, and editorials was undertaken using MEDLlNE, the Cochrane Library databases, and CINAHL from 1947 to November 2010. Search terms were [asthma] and [sickle cell disease]. Additional publications considered relevant to the sickle cell disease population of patients were identified; search terms included [sickle cell disease] combined with [acetaminophen], [pain medications], [vitamin D], [beta agonists], [exhaled nitric oxide], and [corticosteroids]. Results. The reported prevalence of asthma in children with sickle cell disease varies from 2% to approximately 50%. Having asthma increases the risk for developing acute chest syndrome , death, or painful episodes compared to having sickle cell disease without asthma. Asthma and sickle cell may be linked by impaired nitric oxide regulation, excessive production of leukotrienes, insufficient levels of Vitamin D, and exposure to acetaminophen in early life. Treatment of sickle cell patients includes using commonly prescribed asthma medications; specific considerations are suggested to ensure safety in the sickle cell population. Conclusion. Prospective controlled trials of drug treatment for asthma in patients who have both sickle cell disease and asthma are urgently needed.

Asthma and chronic sickle cell lung disease: a dynamic relationship

Chronic lung disease is a significant source of morbidity and mortality in patients with sickle cell disease. Asthma and sickle cell lung disease share many of the same clinical features and pathophysiological mechanisms. Though there is growing evidence of an association between sickle cell disease and airway hyper-reactivity, there is still no consensus on the definition of asthma in sickle cell lung disease. This review will explore what we know about asthma and airway hyper-reactivity in sickle cell disease and whether currently available asthma therapies may be beneficial in delaying or averting the progression of sickle cell lung disease.