Knowledge insufficient: the management of haemoglobin SC disease

Targeted therapeutic management based on phytoconstituents for sickle cell anemia focusing on molecular mechanisms: Current trends and future perspectives

The global epidemic of Sickle cell anemia (SCA) is causing thousands of children to die. SCA, a genetic disorder affecting the hemoglobin-globin chain, affects millions globally. The primary physiological issue in these patients is the polymerization of sickle hemoglobin within their red blood cells (RBCs) during their deoxygenating state. The RBC undergoes a sickle shape due to the polymerization of mutant hemoglobin within it and membrane deformation during anoxic conditions. To prevent complications, it is essential to effectively stop the sickling of RBCs of the patients. Various medications have been studied for treating SCA patients, focusing on antisickling, γ-globulin induction, and antiplatelet action. Natural and synthetic anti-sickling agents can potentially reduce patient clinical morbidity. Numerous clinical trials focused on using natural remedies for the symptomatic therapy of SCA. Medicinal plants and phytochemical agents have antisickling properties. Recent studies on plant extracts' natural compounds have primarily focused on in vitro RBCs sickling studies, with limited data on in vivo studies. This review discussed the potential role of phytoconstituents in the management of SCA.

Seeing haemoglobin SC: Challenging the misperceptions

Historically understudied and regarded as a mild type of sickle cell disease, HbSC can be associated with significant, progressive complications. Prospective studies are urgently needed to address treatment gaps for HbSC disease. Commentary on: Nelson et al. The clinical spectrum of HbSC sickle cell disease-not a benign condition. Br J Haematol 2024;205:653-663.

Sickle cell disease and infertility risks: implications for counseling and care of affected girls and women

INTRODUCTION

Sickle cell disease (SCD), its treatments and cures present infertility risks. Fertility counseling is broadly indicated for affected girls and women and fertility preservation may appeal to some. Several streams of evidence suggest that the reproductive lifespan of women with SCD is reduced. Pregnancy is associated with high miscarriage rates. There are enduring questions about the effects of highly effective hydroxyurea treatment on female fertility. Current conditioning regimens for gene therapy or hematopoietic stem cell transplant are gonadotoxic. Fertility preservation methods exist as non-experimental standards of care for girls and women. Clinicians are challenged to overcome multifactorial barriers to incorporate fertility counseling and fertility preservation care into routine SCD care.

AREAS COVERED

Here we provide a narrative review of existing evidence regarding fertility and infertility risks in girls and women with SCD and consider counseling implications of existing evidence.

EXPERT OPINION

Addressing fertility for girls and women with SCD requires engaging concerns that emerge across the lifespan, acknowledging uncertainty and identifying barriers to care, some of which may be insurmountable without public policy changes. The contemporary SCD care paradigm can offer transformative SCD treatments alongside comprehensive counselling that addresses fertility risks and fertility preservation opportunities.

Systemic medications for sickle cell disease and potential applications for sickle cell retinopathy

PURPOSE OF REVIEW

To review the literature evaluating systemic medications for treatment of sickle cell disease (SCD) and their applications for sickle cell retinopathy.

RECENT FINDINGS

Prior studies have demonstrated the efficacy of traditional systemic therapies in reducing the risk of development of sickle cell retinopathy. Since 2017, several new and promising disease-modifying therapies for sickle cell disease have been approved for clinical use, including the first genetic therapies such as exagamglogene autotemcel (exa-cel) and lovotibeglogene autotemcel (lovo-cel). These treatments have shown promising results for systemic management but are not widely utilized due to limited access and high cost. The efficacy of these therapies for the prevention of sickle cell retinopathy remains unknown and opens the door to new avenues for research. Furthermore, the role of systemic therapy for the management of hemoglobin SC (HbSC) disease, which has milder systemic effects but higher likelihood of causing retinopathy, remains poorly understood.

SUMMARY

Hydroxyurea has been a mainstay of systemic management of SCD with prior work suggesting its ability to reduce the likelihood of developing retinopathy. There are several new and potentially curative systemic therapies for SCD, though their role in retinopathy prevention and management has not been studied extensively. Future studies are necessary to understand the implications of these emerging therapies for sickle cell retinopathy.

Constitutive hypercoagulability in pediatric sickle cell disease patients with hemoglobin SS genotype

Background

Constitutive inflammation and hemostatic activation have been identified as key contributors to the pathophysiology of sickle cell disease (SCD), leading to clinical consequences such as vaso-occlusive crises and stroke. Patients with hemoglobin SS (HbSS) and hemoglobin SC (HbSC) genotypes are reported to have different symptoms, as do patients in steady-state and crisis situations. Differences among these groups remain unclear in pediatric patients.

Objectives

To compare hemostatic activity in HbSS and HbSC pediatric patients during steady state, in crisis, and in clinical follow-up and compare HbSS and HbSC patients with normal healthy children.

Methods

Whole-blood coagulation assay thromboelastography (TEG) was used to assess hemostatic activity. In parallel, flow cytometry was used to assess procoagulant surface expression of platelets and red blood cells.

Results

TEG results indicated no significant differences in clotting onset (R time), clot maximum amplitude, or maximum rate of thrombus generation among steady-state, crisis, and follow-up subgroups of HbSS and HbSC patients. TEG parameters did not differ significantly between HbSC patients and healthy children, while HbSS patients showed significantly shorter R time and greater maximum amplitude and maximum rate of thrombus generation, all indicative of a constitutive hypercoagulable state. Flow cytometry results did not detect increased platelet integrin αIIbβ3 activation or red blood cell procoagulant surface expression in SCD patients compared with unaffected children.

Conclusion

Our results indicate that pediatric SCD patients with the HbSS genotype have constitutively activated hemostasis relative to HbSC patients and healthy children. It remains to be determined how treatments that improve clinical outcomes in SCD patients affect this constitutively hypercoagulable state.

Prospective identification of variables as outcomes for treatment (PIVOT): study protocol for a randomised, placebo-controlled trial of hydroxyurea for Ghanaian children and adults with haemoglobin SC disease

BACKGROUND

Haemoglobin SC (HbSC) is a common form of sickle cell disease (SCD), especially among individuals of West African ancestry. Persons with HbSC disease suffer from the same clinical complications and reduced quality of life that affect those with sickle cell anaemia (HbSS/Sβ0). Retrospective anecdotal data suggest short-term safety and benefits of hydroxyurea for treating HbSC, yet rigorous prospective data are lacking regarding optimal dosing, clinical and laboratory effects, long-term safety and benefits, and appropriate endpoints to monitor. Prospective Investigation of Variables as Outcomes for Treatment (PIVOT) was designed with three aims: (1) to measure the toxicities of hydroxyurea treatment on laboratory parameters, (2) to assess the effects of hydroxyurea treatment on sickle-related clinical and laboratory parameters, and (3) to identify study endpoints suitable for a future definitive phase III trial of hydroxyurea treatment of HbSC disease.

METHODS

PIVOT is a randomised, placebo-controlled, double blind clinical trial of hydroxyurea. Approximately 120 children and 120 adults ages 5-50 years with HbSC disease will be enrolled, screened for 2 months, and then randomised 1:1 to once-daily oral hydroxyurea or placebo. Study treatment will be prescribed initially at 20 ± 5 mg/kg/day with an opportunity to escalate the dose twice over the first 6 months. After 12 months of blinded study treatment, all participants will be offered open-label hydroxyurea for up to 4 years. Safety outcomes include treatment-related cytopenias, whole blood viscosity, and adverse events. Efficacy outcomes include a variety of laboratory and clinical parameters over the first 12 months of randomised treatment, including changes in haemoglobin and fetal haemoglobin, intracranial arterial velocities measured by transcranial Doppler ultrasound, cerebral oxygenation using near infrared spectrometry, spleen volume and kidney size by ultrasound, proteinuria, and retinal imaging. Exploratory outcomes include functional erythrocyte analyses with ektacytometry for red blood cell deformability and point-of-sickling, patient-reported outcomes using the PROMIS questionnaire, and 6-min walk test.

DISCUSSION

For children and adults with HbSC disease, PIVOT will determine the safety of hydroxyurea and identify measurable changes in laboratory and clinical parameters, suitable for future prospective testing in a definitive multi-centre phase III clinical trial.

TRIAL REGISTRATION

PACTR, PACTR202108893981080. Registered 24 August 2021, https://pactr.samrc.ac.za.

Erythrocyte type 1 equilibrative nucleoside transporter expression in sickle cell disease and sickle cell trait

Hypoxia-mediated red blood cell (RBC) sickling is central to the pathophysiology of sickle cell disease (SCD). The signalling nucleoside adenosine is thought to play a significant role in this process. This study investigated expression of the erythrocyte type 1 equilibrative nucleoside transporter (ENT1), a key regulator of plasma adenosine, in adult patients with SCD and carriers of sickle cell trait (SCT). Relative quantitative expression analysis of erythrocyte ENT1 was carried out by Western blot and flow cytometry. Patients with SCD with steady state conditions, either with SS or SC genotype, untreated or under hydroxycarbamide (HC) treatment, exhibited a relatively high variability of erythrocyte ENT1, but with levels not significantly different from normal controls. Most strikingly, expression of erythrocyte ENT1 was found to be significantly decreased in patients with SCD undergoing painful vaso-occlusive episode and, unexpectedly, also in healthy SCT carriers. Promoting hypoxia-induced adenosine signalling, the reduced expression of erythrocyte ENT1 might contribute to the pathophysiology of SCD and to the susceptibility of SCT individuals to altitude hypoxia or exercise to exhaustion.

Dizziness, Falls, and Hearing Loss in Adults Living With Sickle Cell Disease

Objective:

The aim of this study was to assess the prevalence of reported dizziness/imbalance, frequency of falls, and hearing loss in adults with sickle cell disease (SCD) and determine the relationship of these self-reported problems both during and in the absence of an SCD crisis. Also, the impact of educational level and health insurance on seeking treatment services, as well as the relationship of falls to stroke, legal blindness, and other orthopedic problems, was assessed. Interrupted blood flow to shared vestibular and auditory arteries supports the notion of increased likelihood of balance deficits and increased falls in this population.

Design:

A cross-sectional survey study design was used. Adults living with SCD responded to a questionnaire that was distributed online and through traditional mail.

Study Sample:

Adults living with SCD ( N = 135) participated in the study.

Results:

Responses revealed 70% of participants with SCD experienced dizziness/imbalance and 23% reported hearing loss. Furthermore, 33% of participants reported falling one or more times in the last year. The prevalence of dizziness/imbalance, falling, and hearing loss in the respondents with SCD was much higher than that of the general population of the United States. Additionally, for dizziness and falling, the prevalence was higher not only than the national average but also for persons over 65 years of age. A significant association was demonstrated between dizziness/imbalance and hearing loss as well as dizziness/imbalance and falls for adults living with SCD. In fact, participants with self-reported hearing loss were 5.2 times more likely to also report dizziness/imbalance. They were 4.9 times more likely to fall if they also reported dizziness/imbalance. Numbness of the feet was revealed to significantly impact the likelihood of falling in this disease population and should be further studied. Regarding SCD crisis status, dizziness/imbalance and falls were more likely to occur outside of SCD crisis than during a crisis. Furthermore, pain levels were significantly associated with dizziness/imbalance only when respondents were in crisis and not in the absence of a crisis. In crisis, higher pain levels were reported from respondents who also reported dizziness/imbalance than from those who did not report dizziness. No significant relationship was revealed between hearing loss and falls.

Discussion:

These results provide justification for patient and health care provider education regarding appropriate referrals for vestibular/balance assessments and provision of fall prevention strategies. Future studies on balance and SCD are encouraged.

Clinical Presentation of Hemoglobin C in Albania: Case Series

The presence of HbC is a rare event in Europe and Mediterranean region where thalassemia and HbS are more frequently encountered. The rarely diagnosed cases are linked with the migration from West-Central Africa. Albania is one of the Mediterranean countries where inherited haemoglobin disorders are considerably widespread. Studies have shown the presence of thalassemia, sickle cell disease and sporadic cases of Hb O-Arab, Hb Lepore especially in the areas where malaria has been endemic. In 2006 we identified the first case with HbSC disease and until 2020 we have found 15 cases with HbC variant. In this study we have collected and analyzed the laboratory and clinical data of HbC cases. Our data support reports that HbC combinations with HbS and beta thalassemia are clinically important. Our data confirm the presence of the HbC variant in ex-malaric areas where thalassemia and HbS are quite widespread. 

Anemia in the pediatric patient

The World Health Organization estimates that approximately a quarter of the world's population suffers from anemia, including almost half of preschool-age children. Globally, iron deficiency anemia is the most common cause of anemia. Other important causes of anemia in children are hemoglobinopathies, infection, and other chronic diseases. Anemia is associated with increased morbidity, including neurologic complications, increased risk of low birth weight, infection, and heart failure, as well as increased mortality. When approaching a child with anemia, detailed historical information, particularly diet, environmental exposures, and family history, often yield important clues to the diagnosis. Dysmorphic features on physical examination may indicate syndromic causes of anemia. Diagnostic testing involves a stepwise approach utilizing various laboratory techniques. The increasing availability of genetic testing is providing new mechanistic insights into inherited anemias and allowing diagnosis in many previously undiagnosed cases. Population-based approaches are being taken to address nutritional anemias. Novel pharmacologic agents and advances in gene therapy-based therapeutics have the potential to ameliorate anemia-associated disease and provide treatment strategies even in the most difficult and complex cases.

Emerging drugs for the treatment of sickle cell disease: a review of phase II/III trials

INTRODUCTION

The substitution of glutamic acid by valine on the ß-globin gene produces the hemoglobin S variant responsible for sickle cell disease (SCD), a disorder that affects millions of people worldwide and leads to acute and cumulative organ damage. Even though life expectancy has significantly improved where the best medical care is available, there are still few therapeutic options for SCD and those are limited by their availability, cost, and individual toxicities.

AREAS COVERED

This review summarizes the clinical data on current treatments for SCD and emerging therapies studied in the acute setting as well as potential disease-modifying agents, with an emphasis on the FDA-approved agents.

EXPERT OPINION

Hydroxyurea has been a gold standard for two decades, showing benefits in acute complications and overall survival in sickle cell anemia, although data is lacking for certain genotypes such as hemoglobin SC. As progress is made in our understanding of the pathophysiological networks characterizing SCD, numerous pathways appear to be targetable, with L-glutamine, Crizanlizumab and Voxelotor now approved by the FDA. Pursuing a multi-agent approach could alter the disease course in a more effective fashion and provide an alternative option to curative therapies, but longer clinical studies are needed.

Liver Transplant in Hemoglobin SC Disease and Autoimmune Hepatitis: A Case Report

Although liver transplant is a life-saving measure for individuals with end-stage liver disease, the perioperative management may be challenging in individuals with concomitant sickle cell disease. We report a case of a 50-year-old man with sickle cell disease genotype SC (HbSC) and cirrhosis secondary to autoimmune hepatitis who underwent liver transplant. His postoperative course included upper extremity deep vein thrombosis, pulmonary embolus, stroke via a patent foramen ovale after a line removal, and posterior reversible encephalopathy syndrome. Fortunately, he is alive with a functioning graft at 10 months after liver transplant. This case highlights the feasibility of liver transplant in sickle cell disease given the support of meticulous multidisciplinary care and the unique aspects of autoimmune hepatitis and sickle cell disease for liver transplant consideration.

Unusually High Prevalence of Stroke and Cerebral Vasculopathy in Hemoglobin SC Disease: A Retrospective Single Institution Study

INTRODUCTION

Unlike homozygous hemoglobin SS (HbSS) disease, stroke is a rare complication in hemoglobin SC (HbSC) disease. However, recent studies have demonstrated a high prevalence of silent stroke in HbSC disease. The factors associated with stroke and cerebral vasculopathy in the HbSC population are unknown.

METHODS

We conducted a retrospective study of all patients with sickle cell disease treated at the University of Missouri, Columbia, over an 18-year period (2000-2018). The goal of the study was to characterize the silent, overt stroke, and cerebral vasculopathy in HbSC patients and compare them to patients with HbSS and HbS/β thalassemia1 (thal) in this cohort. We also analyzed the laboratory and clinical factors associated with stroke and cerebral vasculopathy in the HbSC population.

RESULTS

Of the 34 HbSC individuals, we found that the overall prevalence of stroke and cerebral vasculopathy was 17.7%. Only females had evidence of stroke or cerebral vasculopathy in our HbSC cohort (33.3%, p = 0.019). Time-averaged means of maximum velocities were lower in the HbSC group than the HbSS group and did not correlate with stroke outcome. Among HbSC individuals, those with stroke and cerebral vasculopathy had a marginally higher serum creatinine than those without these complications (0.77 mg/dL vs. 0.88 mg/dL, p = 0.08). Stroke outcome was associated with recurrent vaso-occlusive pain crises (Rec VOCs) (75 vs. 25%, p = 0.003) in HbSC patients. The predominant cerebrovascular lesions in HbSC included microhemorrhages and leukoencephalopathy.

CONCLUSION

There is a distinct subset of individuals with HbSC who developed overt, silent stroke, and cerebral vasculopathy. A female predominance and association with Rec VOCs were identified in our cohort; however, larger clinical trials are needed to identify and confirm specific clinical and laboratory markers associated with stroke and vasculopathy in HbSC disease.

A Patient With Hemoglobin SC Disease and Acute Ischemic Stroke Presenting With Altered Mental Status

A 57-year-old woman with a history of hypertension, diabetes mellitus, obesity, asthma, and hemoglobin SC disease presented to the emergency department by her home health aide after she was found having altered mental status. According to her home health aide, the patient was responding with "Ok" to her questions for more than a day. The hemoglobin on admission was 8.5 g/dL. A magnetic resonance imaging (MRI) without contrast of the brain showed acute cortical infarcts superimposed on the old infarct zone. The patient received 1 unit of packed red blood cells and a session of exchange transfusion, in addition to aspirin, clopidogrel, and atorvastatin during the hospital stay. When a patient known to have sickle cell disease presents with acute neurological deficits, the first consideration is usually acute ischemic stroke due to vaso-occlusion in the cerebral vessels. However, it is essential to not overlook other potential causes of acute neurological deficits.

Tripartite collaboration of blood-derived endothelial cells, next generation RNA sequencing and bioengineered vessel-chip may distinguish vasculopathy and thrombosis among sickle cell disease patients

Sickle cell disease (SCD) is the most prevalent inherited blood disorder in the world. But the clinical manifestations of the disease are highly variable. In particular, it is currently difficult to predict the adverse outcomes within patients with SCD, such as, vasculopathy, thrombosis, and stroke. Therefore, for most effective and timely interventions, a predictive analytic strategy is desirable. In this study, we evaluate the endothelial and prothrombotic characteristics of blood outgrowth endothelial cells (BOECs) generated from blood samples of SCD patients with known differences in clinical severity of the disease. We present a method to evaluate patient-specific vaso-occlusive risk by combining novel RNA-seq and organ-on-chip approaches. Through differential gene expression (DGE) and pathway analysis we find that BOECs from SCD patients exhibit an activated state through cell adhesion molecule (CAM) and cytokine signaling pathways among many others. In agreement with clinical symptoms of patients, DGE analyses reveal that patient with severe SCD had a greater extent of endothelial activation compared to patient with milder symptoms. This difference is confirmed by performing qRT-PCR of endothelial adhesion markers like E-selectin, P-selectin, tissue factor, and Von Willebrand factor. Finally, the differential regulation of the proinflammatory phenotype is confirmed through platelet adhesion readouts in our BOEC vessel-chip. Taken together, we hypothesize that these easily blood-derived endothelial cells evaluated through RNA-seq and organ-on-chips may serve as a biotechnique to predict vaso-occlusive episodes in SCD patients and will ultimately allow better therapeutic interventions.

A rare case of compartment syndrome and myonecrosis in a patient with hemoglobin SC disease

Myonecrosis and compartment syndrome are rarely seen in sickle cell disease (SCD), and they have not been previously reported in HbSC disease. This case can potentially be recognized as the first case of a patient with HbSC presenting with spontaneous myonecrosis and compartment syndrome.

Oxidative stress, inflammation, blood rheology, and microcirculation in adults with sickle cell disease: Effects of hydroxyurea treatment and impact of sickle cell syndrome

Inflammation and oxidative stress play a key role in the pathophysiology of sickle cell disease (SCD). However, the potential influence of different sickle genotypes, or hydroxyurea (HU) treatment, on these factors remains poorly documented. The present study compared several plasma markers of inflammation and oxidative stress, as well as microvascular function, between patients with sickle SC disease (HbSC, n = 19) and patients with sickle cell anemia (HbSS) under hydroxyurea (HU) treatment (n = 16), or not (n = 13). Hemorheological parameters and levels of inflammatory (IL-6, IL-8, IFN-γ, MCP-1, MIP-1β, TNF-α) and oxidative stress (AOPP, MDA, MPO) markers were determined. Peripheral microcirculatory cutaneous blood flow and immediate microvascular response to local heat were evaluated using laser Doppler flowmetry. Oxidative stress and inflammation were lower in HbSC patients and HbSS patients under HU therapy compared to HbSS patients not treated with HU. Blood viscosity was higher in HbSC than in HbSS patients treated with or not with HU. Vasodilation response of the cutaneous microcirculation to heat stress was higher in HbSS patients receiving HU treatment. Our results clearly established that both sickle cell genotype and HU treatment modulate inflammation and oxidative stress.

Erythrocyte microRNAs: a tiny magic bullet with great potential for sickle cell disease therapy

Sickle cell disease (SCD) is a severe hereditary blood disorder caused by a mutation of the beta-globin gene, which results in a substantial reduction in life expectancy. Many studies are focused on various novel therapeutic strategies that include re-activation of the γ-globin gene. Among them, expression therapy caused by the fetal hemoglobin (HbF) at a later age is highly successful. The induction of HbF is one of the dominant genetic modulators of the hematological and clinical characteristics of SCD. In fact, HbF compensates for the abnormal beta chain and has an ameliorant effect on clinical complications. Erythropoiesis is a multi-step process that involves the proliferation and differentiation of a small population of hematopoietic stem cells and is affected by several factors, including signaling pathways, transcription factors, and small non-coding RNAs (miRNAs). miRNAs play a regulatory role through complex networks that control several epigenetic mechanisms as well as the post-transcriptional regulation of multiple genes. In this review, we briefly describe the current understanding of interactions between miRNAs, their molecular targets, and their regulatory effects in HbF induction in SCD.

Sickle Cell Disease

Sickle cell disease is an umbrella term for a group of hemoglobinopathies characterized by the presence of 2 β-globin gene mutations or deletions, at least 1 of which is the point mutation that leads to the production of hemoglobin S. Sickle cell disease is associated with hemolytic anemia, significant chronic end-organ damage, and early death. In high-income countries, at least 95% of children with the disease survive into adulthood, resulting in a growing population of affected adults with significant comorbidities, complex medical issues, and not enough specialists to provide care. Hydroxyurea is the primary therapy, and recent advances in understanding disease pathophysiology have led to new therapies; progress in bone marrow transplant and gene editing has resulted in cure in some patients. The purpose of this review is to provide an overview of the diagnosis, common acute and chronic clinical manifestations, and best practices for management of sickle cell disease.

Acute Splenic Sequestration Crisis in Hemoglobin SC Disease: Efficiency of Red Cell Exchange

Acute splenic sequestration crisis (ASSC) is recognized as a serious complication of sickle cell disease in children. ASSC presents with progressive splenic enlargement, transfusion-dependent anemia, and, eventually, circulatory compromise. ASSC is rare in adult patients, thus making its management and outcome in adults not well-defined. The purpose of this article is to describe our experience in managing ASSC in an adult female with hemoglobin (Hb) SC disease. The patient underwent an automated red blood cell (RBC) exchange, thus avoiding a planned splenectomy. To the best of our knowledge, our case is the third report in the literature on the use of RBC exchange in adults with HbSC disease and ASSC. RBC exchange should be considered in adults with HbSC disease with ASSC not responding to simple transfusion; a treatment that could alleviate patients' symptoms and avoid splenectomy complications, especially in young patients.

Prevalence of sickle cell disorders and malaria infection in children aged 1-12 years in the Volta Region, Ghana: a community-based study

BACKGROUND

Alterations in the structure of haemoglobin (Hb) are usually brought about by point mutations affecting one or, in some cases, two codons encoding amino acids of the globin chains. One in three Ghanaians are said to have sickle cell disorders, whereas malaria continues to be one of the leading causes of mortality among children. This study determined the prevalence of sickle cell disorders and malaria infection among children aged 1-12 years in the Volta Region.

METHODS

This was a community-based cross-sectional survey that involved 938 children aged 1-12 years selected from three districts, one each from the 3 geographical zones of the Volta Region using a multistage sampling method. Demographic information was collected using a standard questionnaire and anthropometric indices were measured. Isoelectric focusing (IEF) electrophoresis was used to determine the Hb genotypes and sub-microscopic parasites were determined by PCR.

RESULTS

The prevalence of sickling screening positive was 16.0% with an overall prevalence of sickle cell disorders being 2.0%. Among the individual genotypes making up the sickle cell disorders, genotype HbSF was the highest (0.9% as compared to 0.2%; HbSS, 0.6%; HbSC and 0.3%; HbSCF). Microscopic Plasmodium falciparum parasitaemia was detected among 5.5% of the children and 14.2% sub-microscopic prevalence by PCR. Children with sickle cell disorders were more likely to have sub-microscopic parasitaemia (AOR = 5.51 95%CI (2.15, 14.10), p < 0.001) as well as anaemia (AOR = 3.03 95% CI (1.04, 8.82), p = 0.042), compared to those with normal genotypes. There was no significant difference observed between sickle cell disorders and growth and development of the children screened.

CONCLUSIONS

Sickle cell disorders were significantly associated with sub-microscopic parasitaemia as well as anaemia in this study. Establishment of sickle cell clinics in the district and regional hospitals will help in the management of children with the disorder and also generate a national database on sickle cell disorders. National neonatal screening policies must also be put in place to help in early detection and management of these disorders.

Thromboinflammatory mechanisms in sickle cell disease - challenging the hemostatic balance

Sickle cell disease (SCD) is an inherited hemoglobinopathy that is caused by the presence of abnormal hemoglobin S (HbS) in red blood cells, leading to alterations in red cell properties and shape, as the result of HbS dexoygenation and subsequent polymerization. SCD pathophysiology is characterized by chronic inflammatory processes, triggered by hemolytic and vaso-occlusive events, which lead to the varied complications, organ damage and elevated mortality seen in individuals with the disease. In association with activation of the endothelium and leukocytes, hemostatic alterations and thrombotic events are well-documented in SCD. Here we discuss the role for inflammatory pathways in modulating coagulation and inducing platelet activation in SCD, due to tissue factor activation, adhesion molecule expression, inflammatory mediator production and the induction of innate immune responses, amongst other mechanisms. Thromboinflammatory pathways may play a significant role in some of the major complications of SCD, such as stroke, venous thromboembolism and possibly acute chest syndrome, besides exacerbating the chronic inflammation and cellular interactions that trigger vaso-occlusion, ischemia-reperfusion processes, and eventually organ damage.

Acute compartment syndrome in a patient with sickle cell disease

Haemoglobin SC (HbSC) disease accounts for 30% of cases of sickle cell disease in the United Kingdom and the United States. Unlike other sickle cell carriers, who are relatively asymptomatic, people with HbSC disease have a combination of genotypes with the potential to cause considerable morbidity due to intracellular water loss. Patients can present with acute pain, acute chest syndrome, proliferative retinopathy, splenic and renal complications, or stroke. We present a young man with HbSC disease who developed acute compartment syndrome. This is only the second report of this syndrome in a patient with HbSC disease. This is a very rare complication in HbSC disease, but it can have serious implications.

TTP-like syndrome associated with hemoglobin SC disease treated successfully with plasma and red cell exchange

Background

Sickle cell hemoglobinopathies are associated with end organ damage but very rarely present with a clinical and laboratory picture of microangiopathic hemolytic anemia (MAHA) and thrombocytopenia, characteristic of thrombotic microangiopathy (TMA).

Case presentation

We present a patient with HbSC disease who developed thrombotic microangiopathy, needing both RBC exchange transfusion and therapeutic plasma exchange (TPE) for complete clinical recovery.

Conclusion

Although literature showed therapeutic plasma exchange alone can abrogate a similar clinical scenario, we did an in-depth review which concluded that in most of the TMA cases secondary to sickle cell disease, treatment with both with plasma exchange and red cell exchange transfusion are necessary.

Clinical and hematological profile in a newborn cohort with hemoglobin SC

OBJECTIVES

Hemoglobin SC is the second most common variant of sickle-cell disease worldwide, after hemoglobin SS. The objectives of the study were to describe the clinical and laboratory characteristics of hemoglobin SC disease in children from a newborn screening program and treated at a blood center.

METHODOLOGY

This study assessed a cohort of 461 infants born between 01/01/1999 and 12/31/2012 and followed-up until 12/31/2014. Clinical events were expressed as rates for 100 patient-years, with 95% confidence intervals. Kaplan-Meier survival curves were created.

RESULTS

The median age of patients was 9.2 years; 47.5% were female. Mean values of blood tests were: hemoglobin, 10.5g/dL; reticulocytes, 3.4%; white blood cells, 11.24×10⁹/L; platelets, 337.1×10⁹/L; and fetal hemoglobin, 6.3%. Clinical events: acute splenic sequestration in 14.8%, blood transfusion 23.4%, overt stroke in 0.2%. The incidence of painful vaso-occlusive episodes was 51 (48.9-53.4) per 100 patient-years and that of infections, 62.2 episodes (59.8-64.8) per 100 patient-years. Transcranial Doppler ultrasonography (n=71) was normal given the current reference values for SS patients. Hydroxyurea was given to ten children, all of whom improvement of painful crises. Retinopathy was observed in 20.3% of 59 children who underwent ophthalmoscopy. Avascular necrosis was detected in seven of 12 patients evaluated, predominantly in the left femur. Echocardiogram compatible with pulmonary hypertension was recorded in 4.6% of 130 children, with an estimated average systolic pulmonary artery pressure of 33.5mmHg. The mortality rate from all causes was 4.3%.

CONCLUSIONS

Clinical severity is variable in SC hemoglobinopathy. Several children have severe manifestations similar to those with SS disease.

Disorders of erythrocyte hydration

The erythrocyte contains a network of pathways that regulate salt and water content in the face of extracellular and intracellular osmotic perturbations. This allows the erythrocyte to maintain a narrow range of cell hemoglobin concentration, a process critical for normal red blood cell function and survival. Primary disorders that perturb volume homeostasis jeopardize the erythrocyte and may lead to its premature destruction. These disorders are marked by clinical, laboratory, and physiologic heterogeneity. Recent studies have revealed that these disorders are also marked by genetic heterogeneity. They have implicated roles for several proteins, PIEZO1, a mammalian mechanosensory protein; GLUT1, the glucose transporter; SLC4A1, the anion transporter; RhAG, the Rh-associated glycoprotein; KCNN4, the Gardos channel; and ABCB6, an adenosine triphosphate-binding cassette family member, in the maintenance of erythrocyte volume homeostasis. Secondary disorders of erythrocyte hydration include sickle cell disease, thalassemia, hemoglobin CC, and hereditary spherocytosis, where cellular dehydration may be a significant contributor to disease pathology and clinical complications. Understanding the pathways regulating erythrocyte water and solute content may reveal innovative strategies to maintain normal volume in disorders associated with primary or secondary cellular dehydration. These mechanisms will serve as a paradigm for other cells and may reveal new therapeutic targets for disease prevention and treatment beyond the erythrocyte.

Stroke in a Child with Hemoglobin SC Disease: A Case Report Describing use of Hydroxyurea after Transfusion Therapy

Children with hemoglobin SC (HbSC) disease suffer a significant incidence of silent cerebral infarcts but stroke is rare. A 2-year-old African American boy with HbSC disease presented with focal neurologic deficits associated with magnetic resonance imaging evidence of cerebral infarction with vascular abnormalities. After the acute episode he was treated with monthly transfusions and subsequently transitioned to hydroxyurea therapy. The benefits of hydroxyurea as a fetal hemoglobin inducer in HbSC disease, to ameliorate clinical symptoms are supported by retrospective studies. This case highlights the rare occurrence of stroke in a child with HbSC disease and the use of hydroxyurea therapy.