Turf wars: exploring splenomegaly in sickle cell disease in malaria-endemic regions

Unswitched memory B cell deficiency in children with sickle cell disease and response to pneumococcal polysaccharide vaccine

Early mortality in sickle cell disease (SCD) is attributed to increased infections due to loss of splenic function. Marginal zone B cells are important for initial opsonization of pathogens and can be absent in spleen histopathology in SCD. The frequency of unswitched memory B cells (UMBC), the circulating correlate of marginal zone B cells, reflects the immunologic function of the spleen. We hypothesized that asplenia in SCD is associated with alterations in the peripheral blood lymphocyte population and explored whether UMBC deficiency was associated with a clinical phenotype. We analyzed B cell subsets and clinical history for 238 children with SCD and 63 controls. The median proportion of UMBCs was lower in children with SCD compared with controls (4.7% vs. 6.6%, p < .001). Naïve B cells were higher in SCD compared with controls (80.6 vs. 76.3%, respectively, p = .02). UMBC frequency declined by 3.4% per year increase in age in SCD (95% CI: 2%, 4.7%, p < .001), but not in controls. A majority of children in all cohorts had an IgM concentration in the normal range for age and there were no differences between groups (p = .13). Subjects developed titers adequate for long-term protection to fewer serotypes in the polysaccharide vaccine than controls (14.7 vs. 19.4, p < .001). In this cohort, bacteremia was rare and specific clinical complications were not associated with UMBC proportion. In summary, UMBC deficiency occurs in SCD and is associated with age. Future studies should investigate B cell subsets prospectively and identify the mechanism of B cell loss in the spleen.

Exploring the host factors affecting asymptomatic Plasmodium falciparum infection: insights from a rural Burkina Faso study

BACKGROUND

Asymptomatic Plasmodium falciparum parasitaemia forms a reservoir for the transmission of malaria disease in West Africa. Certain haemoglobin variants are known to protect against severe malaria infection. However, data on the potential roles of haemoglobin variants and nongenetic factors in asymptomatic malaria infection is scarce and controversial. Therefore, this study investigated the associations of iron homeostasis, inflammation, nutrition, and haemoglobin mutations with parasitaemia in an asymptomatic cohort from a P. falciparum-endemic region during the high transmission season.

METHODS

A sub-study population of 688 asymptomatic individuals (predominantly children and adolescents under 15 years, n = 516) from rural Burkina Faso previously recruited by the NOVAC trial (NCT03176719) between June and October 2017 was analysed. Parasitaemia was quantified with conventional haemocytometry. The haemoglobin genotype was determined by reverse hybridization assays targeting a selection of 21 HBA and 22 HBB mutations. Demographics, inflammatory markers (interleukins 6 and 10, hepcidin), nutritional status (mid upper-arm circumference and body mass index), and anaemia (total haemoglobin, ferritin, soluble transferrin receptor) were assessed as potential predictors through logistic regression.

RESULTS

Malaria parasites were detected in 56% of subjects. Parasitaemia was associated most strongly with malnutrition. The effect size increased with malnutrition severity (OR = 6.26, CI95: 2.45-19.4, p < 0.001). Furthermore, statistically significant associations (p < 0.05) with age, cytokines, hepcidin and heterozygous haemoglobin S were observed.

CONCLUSIONS

According to these findings, asymptomatic parasitaemia is attenuated by haemoglobin S, but not by any of the other detected genotypes. Aside from evidence for slight iron imbalance, overall undernutrition was found to predict parasitaemia; thus, further investigations are required to elucidate causality and inform strategies for interventions.

Moderate hypoxia induces metabolic divergence in circulating monocytes and tissue resident macrophages from Berkeley sickle cell anemia mice

Introduction

Human and murine sickle cell disease (SCD) associated pulmonary hypertension (PH) is defined by hemolysis, nitric oxide depletion, inflammation, and thrombosis. Further, hemoglobin (Hb), heme, and iron accumulation are consistently observed in pulmonary adventitial macrophages at autopsy and in hypoxia driven rodent models of SCD, which show distribution of ferric and ferrous Hb as well as HO-1 and ferritin heavy chain. The anatomic localization of these macrophages is consistent with areas of significant vascular remodeling. However, their contributions toward progressive disease may include unique, but also common mechanisms, that overlap with idiopathic and other forms of pulmonary hypertension. These processes likely extend to the vasculature of other organs that are consistently impaired in advanced SCD.

Methods

To date, limited information is available on the metabolism of macrophages or monocytes isolated from lung, spleen, and peripheral blood in humans or murine models of SCD.

Results

Here we hypothesize that metabolism of macrophages and monocytes isolated from this triad of tissue differs between Berkley SCD mice exposed for ten weeks to moderate hypobaric hypoxia (simulated 8,000 ft, 15.4% O2) or normoxia (Denver altitude, 5000 ft) with normoxia exposed wild type mice evaluated as controls.

Discussion

This study represents an initial set of data that describes the metabolism in monocytes and macrophages isolated from moderately hypoxic SCD mice peripheral lung, spleen, and blood mononuclear cells.

Prevalence of Splenomegaly and Splenic Complications in Adults with Sickle Cell Disease and Its Relation to Fetal Hemoglobin

Background: Spleen has been found to be the earliest organ involved in sickle cell disease (SCD) patients with variable manifestations in different geographical regions. It usually undergoes autosplenectomy by adolescence but in countries like India, the course of the disease and splenic manifestations are different. And here we aim to study these differences and the relationship between spleen size and fetal hemoglobin (HbF) and various splenic complications in our patients with sickle cell disease. Materials and Methods: This is an observational study of 62 adult patients with sickle cell disease admitted in our prestigious institute in the northwestern part of India, mostly hailing from the tribal population. The clinical and ultrasonographic methods have been used to identify splenomegaly and spleen size and prevalence have been calculated. The correlation coefficient has been calculated between fetal hemoglobin, sickle hemoglobin, and spleen size. Results: The analysis done revealed that 77.4% of patients had abnormal spleen with high average HbF(14.9±5.0) values compared to those who had normal spleen(12.12±4.1). Only 2 patients were found to have no spleen and 3.3% had splenic infarct. All patients with splenomegaly had anemia, 51.6% of patients were in sickle cell crisis and 22.5% were having infections. We also found a weak but positive correlation between spleen size and HbF. Conclusion: This study revealed the persistence of the spleen, the high prevalence of splenomegaly in the Indian adult population with sickle cell disease, and higher levels of fetal hemoglobin, the exact reason for which is still a subject of speculation that needs research. But this paper provides clear evidence of different natural courses of SCD in India.

Pediatric Sickle Cell Disease in Sudan: Complications and Management

Background. Sickle cell disease (SCD) is a life-threatening genetic disorder due to the formation of sickle hemoglobin molecule (HbS) that polymerizes in hypoxic conditions leading to SCD-related complications. Different approaches have been used in the management of SCD including symptomatic management, supportive management, and preventive management. Objectives. To assess the management of SCD in pediatric patients in Gaafar Ibnauf Referral Hospital in Khartoum locality, Sudan. Method. A descriptive, retrospective, hospital-based study was conducted in Gaafar Ibnauf Hospital using a data collection sheet. The study included all medical files of pediatric patients with SCD attending the hospital during the period from the first of April 2018 to the first of July 2018. The data were analyzed using descriptive statistics and the chi-square test. $P<0.05$ was considered statistically significant. Results. Out of 207 pediatric patients, 53.1% were females (mean age of 7.5 ± 3.1 years), with a 1.1 : 1 female:male ratio and low socioeconomic status. Only 4.3% of participants had health insurance. The Messeryia tribe in western Sudan had the highest prevalence of the disease among the Sudanese tribes (11.1%). Vaso-occlusive crisis (33.3%), infections (13.5%), and neurological complications (10.6%) were the most frequent complications reported during routine visits. After initiation of management, only 3.4% of pediatric patients had hemolytic crises, and 1.4% of the anemic patients had splenomegaly. 100% of patients received folic acid, 73.9% used hydroxyurea, and 69.6% underwent blood transfusion for the management of SCD. Prophylactic penicillin was prescribed for 15% of patients, and 41.1% were immunized with pneumococcal vaccine (PPSV23). Most patients had been scheduled for planned follow-up visits every 3–6 months (93.2%). Hydroxyurea and blood transfusion significantly reduced fever and vaso-occlusive crisis. Conclusion. The SCD treatment protocol in Gaafar Ibnauf Children’s Hospital, involving preventive and symptomatic therapy, is consistent with the internationally implemented protocols for SCD management. However, immunization and prophylactic penicillin approaches are deficient.

Splenomegaly in Children and Adolescents

In contrast to other lymphoid tissues making up the immune system, the spleen as its biggest organ is directly linked into the blood circulation. Beside its main task to filter out microorganism, proteins, and overaged or pathologically altered blood cells, also humoral and cellular immune responses are initiated in this organ. The spleen is not palpable during a physical examination in most but not all healthy patients. A correct diagnosis of splenomegaly in children and adolescents must take into account age-dependent size reference values. Ultrasound examination is nowadays used to measure the spleen size and to judge on reasons for morphological alterations in associated with an increase in organ size. An enormous amount of possible causes has to be put in consideration if splenomegaly is diagnosed. Among these are infectious agents, hematologic disorders, infiltrative diseases, hyperplasia of the white pulp, congestion, and changes in the composition and structure of the white pulp by immunologically mediated diseases. This review attempts to discuss a comprehensive list of differential diagnoses to be considered clinically in children and young adolescents.

The spectrum of splenic complications in patients with sickle cell disease in Africa: a systematic review

The majority of the global population of sickle cell disease (SCD) patients resides in Africa. Individuals with this condition are at great risk of serious infections and early mortality secondary to splenic dysfunction without preventative measures. This review investigated the spectrum of splenic complications encountered in SCD among populations in Africa. We systematically searched several databases for all articles published through March 3, 2020. We included 55 studies from 14 African countries. This review reveals the difference in frequency of splenic complications in SCD in Africa when compared with their counterparts in the United State and Europe. While several studies (n = 45) described splenomegaly with a prevalence of 12% to 73% among children, and 4% to 50% among adults with HbSS, the reported prevalence for acute splenic sequestration crisis (n = 6 studies) and hypersplenism (n = 4 studies) was <10% and <5% respectively. A total of 30 surgical splenectomy was reported across eight studies. Only two (3.7%) studies provided data on spleen function. A conflicting pattern was observed amongst studies that evaluated the relationship between splenomegaly and the presence of bacterial and malaria infections. This review reveals the paucity of studies describing the role of SCD-induced splenic dysfunction in morbidity and infection related mortality in Africa.

Insights into determinants of spleen injury in sickle cell anemia

Spleen dysfunction is central to morbidity and mortality in children with sickle cell anemia (SCA). The initiation and determinants of spleen injury, including acute splenic sequestration (ASS) have not been established. We investigated splenic function longitudinally in a cohort of 57 infants with SCA enrolled at 3 to 6 months of age and followed up to 24 months of age and explored the respective contribution of decreased red blood cell (RBC) deformability and increased RBC adhesion on splenic injury, including ASS. Spleen function was evaluated by sequential ^99mTc heated RBC spleen scintigraphy and high-throughput quantification of RBCs with Howell-Jolly bodies (HJBs). At 6 and 18 months of age, spleen filtration function was decreased in 32% and 50% of infants, respectively, whereas the median %HJB-RBCs rose significantly (from 0.3% to 0.74%). An excellent correlation was established between %HJB-RBCs and spleen scintigraphy results. RBC adhesion to laminin and endothelial cells increased with time. Adhesion to endothelial cells negatively correlated with splenic function. Irreversibly sickled cells (ISCs), used as a surrogate marker of impaired deformability, were detected at enrollment and increased significantly at 18 months. %ISCs correlated positively with %HJB-RBCs and negatively with splenic uptake, indicating a relationship between their presence in the circulation and spleen dysfunction. In the subgroup of 8 infants who subsequently experienced ASS, %ISCs at enrollment were significantly higher compared with the asymptomatic group, suggesting a major role of impaired deformability in ASS. Higher levels of %HJB-RBCs were observed after the occurrence of ASS, demonstrating its negative impact on splenic function.

Sickle cell disease and malaria: decreased exposure and asplenia can modulate the risk from Plasmodium falciparum

Background

Patients with sickle cell disease (SCD), an inherited haemoglobinopathy, have increased risk of malaria, at least in part due to impaired splenic function. Infection with Plasmodium falciparum in SCD patients can trigger painful vaso-occlusive crisis, increase the severity of anaemia, and contribute to early childhood mortality.

Case presentation

A 17 year-old Tanzanian male with known SCD was admitted to Muhimbili National Hospital, a tertiary referral centre in Dar-es-Salaam, following an attack of malaria. From 2004 to 2007 the patient had lived in USA, and from 2010 to 2016 in France where, on account of hypersplenism and episodes of splenic sequestrations, in 2014 the spleen was removed. After appropriate clinical and laboratory assessment the patient was re-started on hydroxyurea; and anti-malarial-prophylaxis with proguanil was instituted. The patient has remained well and malaria-free for the following 15 months.

Conclusion

SCD patients are highly vulnerable to malaria infection, and impaired splenic function is a feature of SCD patients, even in those who still anatomically have a spleen. This patient had a surgical splenectomy and, in addition, had probably lost some of the acquired malaria-immunity by having lived for several years in malaria-free areas. This patient is a compelling reminder that long-term anti-malarial prophylaxis should be offered to all patients with SCD who live in malaria-endemic areas.

Consequences of β-Thalassemia or Sickle Cell Disease for Ovarian Follicle Number and Morphology in Girls Who Had Ovarian Tissue Cryopreserved

Women with β-thalassemia (BT) and sickle cell disease (SCD) have a high risk of infertility and premature ovarian insufficiency. Different fertility preserving strategies, including ovarian tissue cryopreservation (OTC) and oocyte cryopreservation has been considered, and healthy babies have been born after successful OTC and transplantation. We evaluated follicle number and follicle health in ovarian tissue from a cohort of BT and SCD patients who underwent OTC before the age of 18 years. Patients undergoing OTC from 2002 to 2019 were included. A total of 14 girls and adolescents with BT and four with SCD, aged 2.8-17.4 years at OTC were included together with a reference group of 43 girls and adolescents with non-anemia diseases considered to have normal ovaries aged 0.6-17.9 years at OTC. Ovarian follicle density was measured in cortex biopsies and compared to the reference group. Expression of proteins associated with follicular health was evaluated using immunohistochemistry. Follicles were detected in the ovarian cortex biopsies from all patients with BT and SCD. The follicle densities were within the 95% prediction interval of the reference group in all cases. A similar expression of six proteins essential for follicular health was detected using immunohistochemistry in BT, SCD, and references. OTC should be considered an option for young girls and adolescents with BT and SCD.

Considering the spleen in sickle cell disease

Introduction: In human physiology, the spleen is generally neglected, and its role is considered anecdotal. In sickle cell disease, splenic dysfunction is the main cause of life-threatening complications, particularly in early childhood with the risk of pneumococcal overwhelming sepsis and acute splenic sequestration crisis, notably. During the course of the disease, the spleen functionally declines and anatomically disappears, albeit with great individual variability depending on modulating genetic and environmental factors. Areas covered: The present review aims to provide an overview of spleen structure and function in order to highlight its role in sickling disorders. The clinical features of spleen damage in sickle cell disease, as well as complications and short- and long-term consequences, are reviewed, along with the main therapeutic options. Expert opinion: Management of acute splenic sequestration recurrence and timing of splenectomy in children with sickling disorders are two main areas in which clinical studies are needed.

Sickle Cell Disease-Genetics, Pathophysiology, Clinical Presentation and Treatment

Sickle cell disease (SCD) is a monogenetic disorder due to a single base-pair point mutation in the β-globin gene resulting in the substitution of the amino acid valine for glutamic acid in the β-globin chain. Phenotypic variation in the clinical presentation and disease outcome is a characteristic feature of the disorder. Understanding the pathogenesis and pathophysiology of the disorder is central to the choice of therapeutic development and intervention. In this special edition for newborn screening for haemoglobin disorders, it is pertinent to describe the genetic, pathologic and clinical presentation of sickle cell disease as a prelude to the justification for screening. Through a systematic review of the literature using search terms relating to SCD up till 2019, we identified relevant descriptive publications for inclusion. The scope of this review is mainly an overview of the clinical features of pain, the cardinal symptom in SCD, which present following the drop in foetal haemoglobin as young as five to six months after birth. The relative impact of haemolysis and small-vessel occlusive pathology remains controversial, a combination of features probably contribute to the different pathologies. We also provide an overview of emerging therapies in SCD.

HAEMATOLOGICAL PROFILE AND BLOOD TRANSFUSION PATTERN OF PATIENTS WITH SICKLE CELL ANAEMIA VARY WITH SPLEEN SIZE

BACKGROUND

The spleen serves critical haematological and immunological functions in the body. However it is also the first organ to be affected by the effects of sickling in sickle cell anaemia. While the splenic size has been evaluated in sickle cell anaemia, the spleen sizes of these patients has not been associated with any specific haematological pattern.

OBJECTIVES

To determine the haematological parameters of patients with sickle cell anaemia (SCA) in relation to spleen size.

METHODS

The full blood count (FBC), the irreversibly sickled cells and blood transfusion use amongst SCA patients in steady state was evaluated. Abdominal ultrasound was also performed for all patients and HbAA control for splenic size categorization.

RESULTS

Forty patients with SCA and 22 controls with HbAA were studied with mean age of 29.28 ± 8.10 years 28.23 ± 8.14 years respectively. The mean splenic longitudinal lengths in patients and controls were 6.3 ± 4.3cm and 8.9 ± 1.5 cm respectively (p-value < .05). The mean haematocrit and haemoglobin value were significantly lower in SCA cases than in controls (p < 0.001). Though the red cell indices were similar but the white blood cell and platelet count were significantly higher in patients than in controls. Among SCA cases, the spleen size showed significant positive correlation with haematocrit (r = 0.371, p = 0.019) and the age at 1^st transfusion (r = 0.447, p = 0.013) but significant negative correlation with MCV, MCH, MCHC and platelet count. Above 80% of patients with severe, moderate and mild autosplenectomy had been transfused compared to 25% of patients with splenomegaly.

CONCLUSION

Similarities in red cell indices between patients and controls suggests an identical factor influencing the red cell indices which could be genetic such as thalassemia or environmental such as iron deficiency. The negative correlation of the spleen size with red cell indices, white cell count and platelet count and positive correlation with haematocrit suggest that spleen size can be used to determine clinical course of the disease. Earlier age at first transfusion, significantly higher frequency of blood transfusion and MCHC in patients with severe autosplenectomy suggest a more severe clinical course when compared with patients with splenomegaly, normal spleen, mild and moderate autosplenomegaly.

Children with sickle cell disease migrating to the United States from sub-Saharan Africa

Sickle cell disease (SCD) is an inherited red blood cell disorder that occurs worldwide and results in significant morbidity and mortality. In addition to affected children who are born in the US, an increasing number of children with SCD are migrating to the US with their families or through international adoption. Children arriving as immigrants or refugees have unique medical and psychosocial challenges that require a multidisciplinary team approach which takes into account the family's primary language, culture, and health beliefs. This review focuses on the special challenges for children with SCD who emigrate from sub-Saharan Africa to the US.

Prescription audit in a paediatric sickle cell clinic in South-West Nigeria: A cross-sectional retrospective study

Background

Sickle cell disease (SCD) is a genetic haematological disorder that affects millions of people around the world especially people of African heritage. The treatment of the symptoms of SCD includes the use of analgesics, antibiotics, and anti-malarial drugs. Studying the pattern of drug prescription is a veritable tool for establishing the current practice and how it conforms to existing guidelines.

Objectives

The main objective of this study was to assess the pattern of drug prescription in children with sickle cell disease (SCD) attending the paediatric outpatients' clinic of a tertiary care centre in Ado-Ekiti, South-West Nigeria.

Methods

This was a cross-sectional retrospective study carried out using the medical records of all patients with SCD who attended the paediatric outpatient clinic of the teaching hospital between January 1 and December 31, 2014. The information retrieved from the case notes included the bio-demographic data, associated co-morbid conditions and the list of prescribed drugs.

Results

A total of 202 SCD patients aged below 18 years were seen in the clinic during the study period with males accounting for 61.9% of them. The mean age of all patients was 6.9 ±3.8 yrs. A total of 1015 medications were prescribed during the study period giving a mean of 5.02 ± 1.9. Vitamins/micronutrients, anti-malarial drugs, antibiotics and analgesics accounted for 41.4%, 29.0%, 15.7% and 13.9% of all prescribed drugs respectively. Antibiotics from the penicillin group were the most commonly prescribed followed by macrolides and cephalosporins while Ibuprofen (60.3%) and Acetaminophen (32.6%) were the commonly prescribed analgesics.

Conclusion

High rate of antibiotic prescription, low use of opioid analgesics and non-prescription of prophylactic penicillin/pneumococcal vaccination were the main findings in this study. There is need for the introduction of standard treatment protocols for this group of patients.