Mixed donor chimerism following stem cell transplantation for sickle cell disease

Sickle cell disease is a debilitating hemoglobinopathy with high morbidity and mortality. Hematopoietic stem cell transplantation (HCT) is curative, but the presence of mixed donor/recipient chimerism post-HCT raises concerns about disease control long-term. Mixed donor/recipient chimerism is reported in significant numbers even after aggressive HCT conditioning regimens. Post-HCT, adequacy of donor erythropoiesis is crucial for disease control. This review explores the relationship between mixed donor/recipient chimerism and outcomes post-HCT. Serial chimerism analysis in lineage specific manner in erythroid or myeloid cells post-HCT predicts for disease control and HCT success. Adequate and stable donor-derived erythropoiesis is essential for reversing SCD manifestations. Myeloid lineage chimerism mirrors erythropoiesis is commercially available, and a reliable indicator of adequacy. Using this tool, the minimum threshold of donor chimerism is required to prevent SCD-related complications and maintain sickle hemoglobin less than 50% is approximately 20-25% even when a donor has Hb S trait. Curative interventions should, at a minimum, meet this goal long-term. Achieving a balance between successful engraftment while minimizing toxicity is important in patients vulnerable because of age or preexisting morbidity and is the objective of recent clinical trials. As HCT and gene therapies evolve, efficient long-term follow-up that includes durability assessment of mixed donor/recipient chimerism will be crucial.

Understanding Sickle cell disease: Causes, symptoms, and treatment options

Sickle cell disease (SCD) is a hereditary blood disorder characterized by the production of abnormal hemoglobin molecules that cause red blood cells to take on a crescent or sickle shape. This condition affects millions of people worldwide, particularly those of African, Mediterranean, Middle Eastern, and South Asian descent. This paper aims to provide an overview of SCD by exploring its causes, symptoms, and available treatment options. The primary cause of SCD is a mutation in the gene responsible for producing hemoglobin, the protein that carries oxygen in red blood cells. This mutation has abnormal hemoglobin called hemoglobin S, which causes red blood cells to become stiff and sticky, leading to various health complications. Patients with SCD may experience recurrent pain, fatigue, anemia, and increased infection susceptibility. Treatment options for SCD focus on managing symptoms and preventing complications. This includes pain management with analgesics, hydration, and blood transfusions to improve oxygen delivery. Hydroxyurea, a medication that increases the production of fetal hemoglobin, is commonly used to reduce the frequency and severity of pain crises. Additionally, bone marrow or stem cell transplants can cure select individuals with severe SCD. Finally, understanding the causes, symptoms, and treatment options for SCD is crucial for healthcare professionals, patients, and their families. It enables early diagnosis, effective symptom management, and improved quality of life for individuals with this chronic condition.

Secondary Neoplasms After Hematopoietic Cell Transplant for Sickle Cell Disease

PURPOSE

To report the incidence and risk factors for secondary neoplasm after transplantation for sickle cell disease.

METHODS

Included are 1,096 transplants for sickle cell disease between 1991 and 2016. There were 22 secondary neoplasms. Types included leukemia/myelodysplastic syndrome (MDS; n = 15) and solid tumor (n = 7). Fine-Gray regression models examined for risk factors for leukemia/MDS and any secondary neoplasm.

RESULTS

The 10-year incidence of leukemia/MDS was 1.7% (95% CI, 0.90 to 2.9) and of any secondary neoplasm was 2.4% (95% CI, 1.4 to 3.8). After adjusting for other risk factors, risks for leukemia/MDS (hazard ratio, 22.69; 95% CI, 4.34 to 118.66; P = .0002) or any secondary neoplasm (hazard ratio, 7.78; 95% CI, 2.20 to 27.53; P = .0015) were higher with low-intensity (nonmyeloablative) regimens compared with more intense regimens. All low-intensity regimens included total-body irradiation (TBI 300 or 400 cGy with alemtuzumab, TBI 300 or 400 cGy with cyclophosphamide, TBI 200, 300, or 400 cGy with cyclophosphamide and fludarabine, or TBI 200 cGy with fludarabine). None of the patients receiving myeloablative and only 23% of those receiving reduced-intensity regimens received TBI.

CONCLUSION

Low-intensity regimens rely on tolerance induction and establishment of mixed-donor chimerism. Persistence of host cells exposed to low-dose radiation triggering myeloid malignancy is one plausible etiology. Pre-existing myeloid mutations and prior inflammation may also contribute but could not be studied using our data source. Choosing conditioning regimens likely to result in full-donor chimerism may in part mitigate the higher risk for leukemia/MDS.

Atomic force microscopy reveals involvement of the cell envelope in biomechanical properties of sickle erythrocytes

BACKGROUND

Intracellular hemoglobin polymerization has been supposed to be the major determinant for the elevated rigidity/stiffness of sickle erythrocytes from sickle cell anemia (SCA) patients. However, the contribution of the cell envelope remains unclear.

RESULTS

In this study, using atomic force microscopy (AFM), we compared the normal and sickled erythrocyte surfaces for stiffness and topography. AFM detected that sickle cells had a rougher surface and were stiffer than normal erythrocytes and that sickle cell ghosts had a rougher surface (for both outer and inner surfaces) and were thicker than normal ghosts, the latter implying a higher membrane-associated hemoglobin content/layer in the sickle cell envelope. Compared to healthy subjects, the SCA patients had lower plasma lipoprotein levels. AFM further revealed that a mild concentration of methyl-β-cyclodextrin (MβCD, a putative cholesterol-depleting reagent) could induce an increase in roughness of erythrocytes/ghosts and a decrease in thickness of ghosts for both normal and sickle cells, implying that MβCD can alter the cell envelope from outside (cholesterol in the plasma membrane) to inside (membrane-associated hemoglobin). More importantly, MβCD also caused a more significant decrease in stiffness of sickle cells than that of normal erythrocytes.

CONCLUSIONS

The data reveal that besides the cytosolic hemoglobin fibers, the cell envelope containing the membrane-associated hemoglobin also is involved in the biomechanical properties (e.g., stiffness and shape maintenance) of sickle erythrocytes.

Mortality and Causes of Death From Sickle Cell Disease in The Netherlands, 1985-2017

In the Netherlands, between 1985 and 2007 secular changes in the health care of patients with sickle cell disease (SCD) have taken place, such as penicillin prophylaxis, vaccination programs and stroke prevention. We investigated the number and causes of death in a cohort of 298 SCD patients, established in 2007, before introduction of neonatal screening, to determine preventable deaths. All patients were diagnosed with SCD before the age of 18 (median age at diagnosis 5.1 y). Their vital status was determined up to January 2017. After a total follow-up period of 4565 patient years and a median time of follow-up of 15 years for all patients, 230 patients (77%) were still alive, 45 patients (15%) were lost to follow-up and a total of 23 patients (8%) had died. Estimated survival to 18 years was 92% with a global mortality rate of 0.48 deaths/100 patient years. Leading causes of death were infection (35%) followed by neurologic complications (22%) and death in the course of a painful episode (13%). Nine of the 20 known causes of death were preventable. These results strongly suggest the benefit of comprehensive care measures for patients with SCD in the Netherlands to further prevent morbidity and mortality.

Racial mixture, blood and nation in medical publications on sickle cell disease in 1950s Brazil

This paper investigates continuities and changes in the definition of sickle cell disease in 1950s Brazil, taking into account that diseases have a history and are recognized as such according to the knowledge and perceptions available in a certain historical period and specific location. In the post-war era, new diagnostic tools, inheritance theories and, in particular, discussions on the concepts of race and racial relations, both nationally and internationally, were changing previous racialist and racist views. Nonetheless, the Brazilian medical interpretations of sickle cell disease continued to racialize it and even use deep-rooted racist formulations to explain its symptoms or the existence of the disease. It is argued that the celebration of racial mixture and racial democracy might have concealed racist presumptions biasing the study of sickle cell disease. Although race as a biological concept gradually gave way to other genetic expressions, in Brazilian medical papers on sickle cell disease, race continued to influence the interpretation of the disease, along with the persistence of concepts of heredity through blood mixture.

The Importance of Demodex Mites (Acari: Demodicidae) in Patients With Sickle Cell Anemia

Although demodicosis caused by Demodex folliculorum and Demodex brevis is widely seen throughout the world, the pathogenic mechanisms are not fully known. To the best of our knowledge, the effect of Demodex mites in patients with sickle cell anemia (SCA) is not known. SCA is a genetic disease characterized by abnormal hemoglobin production and suppression of the immune system. The aim of this study was to determine the prevalence and Demodex density in SCA patients and to compare with healthy subjects. The study included 70 patients diagnosed with SCA and control group of 50 healthy individuals. Samples were taken from cheeks, forehead, nose, and chin and were examined microscopically. Infestation of ≥5 mites/cm2 was accepted as positive in the diagnosis. Demodex mite positivity was determined in 20 (28.6%) patients and none in subjects of the control group. In the SCA group, the mean number of mites was 26.10/cm2. A statistically significant correlation was found between Demodex mite positivity and the number of SCA symptom attacks experienced by the patients within the last 1 yr (P ≤ 0.001). No significant relationship was determined between Demodex mite positivity and age or gender (P = 0.56 and P = 0.11, respectively). Demodex mites are seen more often in SCA patients who suffer from a compromised immune system, and the presence of Demodex mites could be a risk factor in the appearance of SCA symptom attacks.

Synergistic Integration of Laboratory and Numerical Approaches in Studies of the Biomechanics of Diseased Red Blood Cells

In red blood cell (RBC) disorders, such as sickle cell disease, hereditary spherocytosis, and diabetes, alterations to the size and shape of RBCs due to either mutations of RBC proteins or changes to the extracellular environment, lead to compromised cell deformability, impaired cell stability, and increased propensity to aggregate. Numerous laboratory approaches have been implemented to elucidate the pathogenesis of RBC disorders. Concurrently, computational RBC models have been developed to simulate the dynamics of RBCs under physiological and pathological conditions. In this work, we review recent laboratory and computational studies of disordered RBCs. Distinguished from previous reviews, we emphasize how experimental techniques and computational modeling can be synergically integrated to improve the understanding of the pathophysiology of hematological disorders.

Perinatal and Neonatal Implications of Sickle Cell Disease

Sickle cell disease is the genetic disorder most commonly detected with state-mandated newborn screening. Women with sickle cell disease struggle with psychosocial, emotional, and physical challenges throughout their lives. Pregnancy for women with sickle cell disease brings greater risk for maternal and fetal morbidity and mortality and increased likelihood of hospitalization for complications, including sickle cell pain crisis. Chronic maternal opioid use for pain can place newborns at risk for neonatal abstinence syndrome. Care of a pregnant woman with sickle cell disease requires a collaborative, multidisciplinary team addressing the medical, social, and emotional needs of the woman and her family.

Elevated sphingosine-1-phosphate promotes sickling and sickle cell disease progression

Sphingosine-1-phosphate (S1P) is a bioactive lipid that regulates multicellular functions through interactions with its receptors on cell surfaces. S1P is enriched and stored in erythrocytes; however, it is not clear whether alterations in S1P are involved in the prevalent and debilitating hemolytic disorder sickle cell disease (SCD). Here, using metabolomic screening, we found that S1P is highly elevated in the blood of mice and humans with SCD. In murine models of SCD, we demonstrated that elevated erythrocyte sphingosine kinase 1 (SPHK1) underlies sickling and disease progression by increasing S1P levels in the blood. Additionally, we observed elevated SPHK1 activity in erythrocytes and increased S1P in blood collected from patients with SCD and demonstrated a direct impact of elevated SPHK1-mediated production of S1P on sickling that was independent of S1P receptor activation in isolated erythrocytes. Together, our findings provide insights into erythrocyte pathophysiology, revealing that a SPHK1-mediated elevation of S1P contributes to sickling and promotes disease progression, and highlight potential therapeutic opportunities for SCD.

Treatment of acute ischemic stroke: beyond thrombolysis and supportive care

The initial therapeutic approach to acute ischemic stroke consists of thrombolytic therapy and early initiation of supportive care, usually commenced prior to the determination of the underlying stroke etiology. Varying stroke mechanisms may call for specific, etiology-based treatment. The majority of strokes result from cardioembolism, large-vessel atherothromboembolism, and small-vessel occlusive disease. There are scant data to support the use of acute anticoagulation therapy over anti-platelet therapy in cardioembolic stroke and large-vessel atherosclerosis, although it may be reasonable in a certain subset of patients. However, augmentation of blood flow with early surgery, stenting, or induced hypertension, may play a role in patients with large artery stenosis. The less commonly identified stroke mechanisms may warrant special consideration in treatment. Controversy remains regarding the optimal anti-thrombotic treatment of arterial dissection. Reversible cerebral vasoconstriction syndrome may benefit from therapy with calcium channel blockers, high-dose steroids, or magnesium, although spontaneous recovery may occur. Inflammatory vasculopathies, such as isolated angiitis of the central nervous system and temporal arteritis, require prompt diagnosis as the mainstay of therapy is immunosuppression. Cerebral venous thrombosis is a rare cause of stroke, but one that needs early identification and treatment with anticoagulation. Rapid determination of stroke mechanism is essential for making these critical early treatment decisions.

Absence of association between TNF-α polymorphism and cerebral large-vessel abnormalities in adults with sickle cell anemia

Stroke is a serious complication of sickle cell anemia (SCA) affecting children and adults. Recent reports suggested that tumor necrosis factor-α (TNF-α) (-308) polymorphism is an important risk factor for stroke in children with SCA. The role of TNF-α polymorphism in the frequency of brain magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) abnormalities in adults with SCA is still uncertain. Our objective was to evaluate the frequency of TNF-α polymorphism in adults with SCA and to correlate it to brain MRI and MRA findings. TNF-α (-308) polymorphism was determined in 49 adults with SCA. All subjects were evaluated with brain MRI/MRA to establish the presence of intracranial abnormalities. Thirty-three (67.3%) had abnormal brain MRA scans, 8 (16.3%) had intracranial stenosis and 29 (59.2%) showed arterial tortuosity. Forty-one (83.7%) had the GG genotype and 8 had the GA genotype. There was no correlation between homozygosity for G allele and MRA or MRI abnormalities. Although TNF-α (-308) polymorphism is a potential predictor of the genetic risk for stroke in children, we found no association between the polymorphism and large vessel abnormalities in adults with SCA.

Total antioxidants status and some hematological values in sickle cell disease patients in steady state

Congenital hemoglobin mutations may alter the delicate balance of free-radical generation and antioxidant defense systems in the red cell. Oxidative stress may thus play a role in the pathophysiology of the clinical manifestations of the disease. We assessed the total antioxidant status in steady-state sickle cell anemia (SCA) patients and related it to certain hematological parameters and their recent clinical history. Forty (25 males/15 females) adult SCA patients and 30 age-matched controls were studied. All patients and control subjects had total antioxidant status (TAS), hematocrit, white blood cells, platelets and reticulocyte count done. The results showed that TAS levels were about 50% lower in the SCA patients compared with the controls. Among the SCA patients, 57.1% of those with TAS levels <1.00 mmol/L had bone pain crisis >3 times in the past year, compared with 16% in those with TAS levels >1.00 mmol/L. Total leukocyte count and platelets were also significantly higher in the SCA patients than controls. Our data support the growing evidence that oxidative stress has a role to play in the pathophysiology of SCA and intervention aimed at increasing the antioxidant capacity of these patients may be beneficial.

Antioxidant vitamin levels in sickle cell disorders

BACKGROUND

Sickle cell disorder is a haemoglobinopathy prevalent in the Vidharbha region of Maharashtra, central India. With recent evidence of oxidative stress in sickle haemoglobinopathy, a possible deficiency of antioxidant vitamins was suspected.

METHODS

We measured plasma vitamin E, vitamin C and beta-carotene levels in persons with heterozygous (n=80) and homozygous sickle cell state (n=20), and suitable healthy controls for these groups (n=100 and 66, respectively) in a community-based study in the villages near our institution.

RESULTS

Subjects with heterozygous sickle cell trait had lower vitamin E levels than their respective controls (p < 0.05). Subjects with homozygous sickle cell disease had lower levels of all three vitamins (p < 0.05). Vitamins E and C levels showed a significant positive correlation in both forms of sickle cell disorder.

CONCLUSION

Our findings suggest that there is depletion of the antioxidant vitamins, particularly in severe forms of sickle cell disorder. A trial of administration of therapeutic doses of vitamin E in this condition is warranted.

Blood Transfusions Leading to Apparent Hemoglobin C, S, and O-Arab Hemoglobinopathies

Context.—Apparent hemoglobinopathies caused by blood transfusions rarely have been reported in the scientific literature.

Objective.—To interpret the abnormal hemoglobins appearing as small peaks on hemoglobin chromatograms or electrophoresis membranes.

Design.—In the clinical laboratories of a university hospital and a metropolitan hospital affiliated with a medical school, we interpreted hemoglobin chromatograms and electrophoresis membranes; correlated them with patients' medical, laboratory, and transfusion records; and when possible, identified the abnormal hemoglobin in the donors' transfusion segments.

Results.—We detected 52 incidences of apparent hemoglobinopathies in 32 recipients caused by blood transfusion, of which 46 were hemoglobin C, 4 were hemoglobin S, and 2 were hemoglobin O-Arab. When first detected, the abnormal hemoglobins in recipients ranged from 0.8% to 14% (median, 5.6%). Multiple transfusions with abnormal hemoglobins occurred in 11 patients with 2 patients receiving hemoglobin C blood 5 separate times. One patient received hemoglobin C and later S, and another patient received C and later O-Arab.

Conclusions.—Apparent hemoglobinopathies caused by blood transfusions are far more common than previously reported and represent diagnostic challenges. Misdiagnosis could lead to unnecessary testing, treatment, and counseling. If a hemoglobinopathy from a unit of transfused blood is identified in a recipient, we recommend notifying the donor of that abnormality.

[Hematological and clinical profile in sickle cell or thalassemic patients]

Clinical and hematological characteristics of 14 patients with sickle cell anemia; one heterozygous AS, and 7, with diagnostic of microcytic hypochromic anemia were analyzed. Hemoglobin phenotypes were identified by electrophoresis, fetal hemoglobin was quantificated for alkaline denaturation and the HbA2 for ionic exchange chromatography; -alpha3,7 -thalassemia was detected by mutation identification using polymerase chain reaction (PCR). SS phenotype was confirmed in 10 patients, two were SSF increased, one was SSFincreasedA2increased, and one was ASFincreased (HbF = 2%). The patient diagnosed as AS was SSFincreased (HbF = 21%). AD-patients presented a moderate clinical course of the illness. Five microcytic hypochromic anemia patients were HbAA, one was HbAAA2increased and another HbAAFincreased; those patients present a high hematological and clinical variation. beta-thalassemia was 19%. -alpha3,7-thalassemia was not detected. Infection was most frequent clinical manifestation (respiratory tract infection and intestinal parasitism). These results shows that -alpha3,7-thalassemia are not modulator genetic factors of clinical and hematological manifestations of patients with microcytic hypochromic anemia and sickle cell anemia. We suggest that environmental factors such as respiratory tract infection and intestinal parasitism may be affect the course of illness.

Laparoscopic cholecystectomy in children with chronic hemolytic anemia. Is the outcome related to the timing of the procedure?

BACKGROUND

The aim of this study was to evaluate whether the outcome in children with chronic hemolytic anemia (CHA) and cholelithiasis undergoing laparoscopic cholecystectomy (LC) is related to the operation timing.

METHODS

From June 1995 to December 2004, 46 children with CHA were referred to our division of surgery for cholelithiasis. All 46 children were asymptomatic at the time of the first visit, and an elective LC was proposed to all of them before the onset of symptoms. The operation was accepted in the period of study by 24 children and refused by 22. The patients were divided into three groups (group A, asymptomatic; group B, symptomatic; and group C, emergency admitted) depending on clinical presentation and operation timing, and the respective outcomes were compared.

RESULTS

Elective LC in asymptomatic children (group A) is safe with no major complications reported. In children who refused surgery (groups B and C), we observed four sickle cell crises, four acute cholecystitis, and two choledocholithiasis, and all these complications were related to waiting. Two sickle cell crises occurred in symptomatic children waiting for surgery during biliary colic. The risk of emergency admission in children with cholelithiasis and CHA awaiting surgery was found to be high: 28% of the children admitted in emergency after a mean of 32 months (range, 22-36). Morbidity rate and postoperative stay increased when children with hemoglobinopathies underwent emergency LC.

CONCLUSIONS

Elective LC should be the gold standard in children with CHA and asymptomatic cholelithiasis in order to prevent the potential complications of cholecystitis and choledocholithiasis, which lead to major risks, discomfort, and longer hospital stay.

Understanding sickle cell disorders

More than 12,500 people in England have sickle cell disorders. This article explains how these disorders call be inherited and discusses the associated clinical problems. The author focuses on social, psychosocial and cultural aspects, and the implications for nursing practice are examined.

Sickle cell anaemia 1: background, causes and incidence in the UK

Sickle cell anaemia (SCA) and beta thalassaemia are severe inherited blood disorders. Despite some reports indicating that haemoglobinopathies are the most common serious genetic disorder in the UK, some parts of Europe, Africa and the Caribbean, sickle cell disorders still receive relatively little attention from the public or the healthcare service industry. The aim of this article, the first of two parts, is to provide an overview to the background, causes and incidence of sickle cell disorders in the UK and how an acute crisis state develops. Readers should note that the term 'painful episode' is now used in preference to 'crisis', which suggests catastrophe. The second article will look more closely at the pharmacological treatments for SCA painful episode management.

Cerebrovascular disorders

Arterial ischemic stroke is being recognized more commonly in the pediatric population. The etiologies differ greatly from those seen in adults. The most common etiologies are congenital heart disease and sickle cell disease. Children may present with or without hemiparesis and may have fever, headache, and depressed level of consciousness. A high index of suspicion is needed to diagnose stroke. Although clinical studies are scarce in children, besides early diagnosis, early specialized care with careful attention to detail ensuring adequate oxygenation and ventilation, prevention of hyperthermia and seizures, and maintenance of blood pressure and metabolic balance are important and likely improve outcome in these children. Selective children may also benefit from anticoagulant therapy, and, as the interval to diagnosis decreases, thrombolytic therapy may become an option although safety data are required. Children with acute stroke should be rapidly transported to and cared for in a pediatric center with a specialized stroke team or access to acute stroke protocols.

Anti-sickling effect of MX-1520, a prodrug of vanillin: anin vivostudy using rodents

Vanillin, a food additive, covalently binds with sickle haemoglobin (Hb S), inhibits cell sickling and shifts the oxygen equilibrium curve towards the left. These effects would potentially benefit patients with sickle cell disease (SCD). However, vanillin has no therapeutic effect if given orally because orally administered vanillin is rapidly decomposed in the upper digestive tract. To overcome this problem, a vanillin prodrug, MX-1520, which is biotransformed to vanillin in vivo, was synthesized. Studies using transgenic sickle mice, which nearly exclusively develop pulmonary sequestration upon exposure to hypoxia, showed that oral administration of MX-1520 prior to hypoxia exposure significantly reduced the percentage of sickled cells in the blood. The survival time under severe hypoxic conditions was prolonged from 6.6 +/- 0.8 min in untreated animals to 28.8 +/- 12 min (P < 0.05) and 31 +/- 7.5 min (P < 0.05) for doses of 137.5 and 275 mg/kg respectively. Intraperitoneal injection of MX-1520 to bypass possible degradation in the digestive tract showed that doses as low as 7 mg/kg prolonged the survival time and reduced the percentage of sickled cells during hypoxia exposure. These results demonstrate the potential for MX-1520 to be a new and safe anti-sickling agent for patients with SCD.

Impact of environmental tobacco smoke on children with sickle cell disease

BACKGROUND

Parallels between the biological effects of exposure to environmental tobacco smoke (ETS) on nonsmokers and the pathophysiology of sickle cell disease (SCD) suggest that complications of SCD could be exacerbated by ETS exposure.

OBJECTIVE

To determine whether children with SCD who are exposed to ETS at home have more sickle cell crises than do those who live in nonsmoking households.

DESIGN

A retrospective cohort study in which ETS exposure was measured by using a survey of caretakers and patients.

SETTING

A university-based pediatric sickle cell center.

PARTICIPANTS

Fifty-two of 66 eligible children aged 2 to 18 years with SCD.

OUTCOME MEASURES

The number of sickle cell vaso-occlusive crises requiring hospitalization per patient during the 2-year study (inpatient sickle cell crises). Total hospital days and hospital costs were secondary outcome measures.

RESULTS

Patients exposed to ETS had more inpatient sickle cell crises than did unexposed patients (mean +/- SD, 3.7 +/- 5.7 vs 1.7 +/- 3.5; P =.02), and this association retained significance after adjustment for important covariates (risk ratio, 1.9; 95% confidence interval, 1.3-2.7). Hospital costs were greater in the exposed group than in the unexposed group (mean +/- SD, 21,671 US dollars +/- 41,809 US dollars vs 9705 US dollars +/- 19 146 US dollars; effect estimate, 11.4; 95% confidence interval, 1.0-129.5).

CONCLUSIONS

Children with SCD who are exposed to ETS have a higher risk of sickle cell crises requiring hospitalization than do those not exposed, independent of other factors known to increase the frequency of sickle cell crises. Decreasing the exposure of these children to ETS could reduce morbidity and may provide cost savings.

Temperature changes, temperature extremes, and their relationship to emergency department visits and hospitalizations for sickle cell crisis

Weather changes are among the proposed precursors of painful sickle cell crises. However, epidemiologic data are mixed regarding the relationship between ambient temperature and crisis frequency. To study this relationship among a local sickle cell disease population, emergency department (ED) visits and admissions were evaluated in adults with sickle cell crisis as the primary diagnosis at a major teaching hospital in a temperate climate. Official daily ambient temperatures (average for that day) were obtained from the National Climate Data Center for the days patients visited the ED or were hospitalized, and for 24 or 48 hours prior. Daily ED visit counts and admission counts were correlated with the visit/admission day's ambient temperature, with the ambient temperature 24 hours before admission, and with the magnitude of change in daily ambient temperature over the prior 24 or 48 hours. For all correlations, statistical significance was defined as a p value of <0.01 and clinical significance was defined as a moderate or greater correlation, absolute value of r >/= 0.30. ED visits or admissions correlated statistically, but not clinically, with daily temperatures. On days when temperatures were <32 degrees F or >80 degrees F, these correlations were statistically significant, but clinical significance was variable. ED visits or admissions correlated only statistically with temperatures 24 hours prior, even on days when temperatures were <32 degrees F. When temperatures were >80 degrees F, the correlations were statistically significant, but there was a reverse, clinically significant correlation between admissions and temperatures. Finally, only statistically significant correlations were found between ED visits or admissions and change in temperature over the prior 24 or 48 hours. Weak or inconsistent confirmation of a relationship was found between daily ambient temperatures and ED visits or hospital admissions for sickle cell crises.

Niprisan (Nix-0699) improves the survival rates of transgenic sickle cell mice under acute severe hypoxic conditions

The substitution of glutamic acid by valine at the sixth position of the beta-globins of haemoglobin S (Hb S) causes a drastic reduction in the solubility of the deoxy form of Hb S. Under hypoxic conditions, deoxy-Hb S molecules polymerize inside the cells, forming rigid, sickled cells. We studied the effect of Niprisan (Nix-0699), a naturally occurring antisickling agent, on the survival of transgenic (Tg) sickle mice under severe acute hypoxic conditions (60 min). Before hypoxia exposure, the mice were treated by gavage once daily for 7 d with 0 mg/kg (n = 10), 10 mg/kg (n = 5), 50 mg/kg (n = 5), 300 mg/kg (n = 4) or 500 mg/kg (n = 5) of Nix-0699. The mean survival times of the untreated and treated mice were 10, 25, 39, 55 or 60 min respectively. The percentage of sickled cells in the venous blood of the treated mice was lower than that in control mice and was dose dependent. Histological examination of the lungs of the control mice showed entrapment of massive numbers of sickled cells in the alveolar capillaries, although the degree of such entrapment decreased with the increased dose of Nix-0699. Nix-0699 may be a promising option for the treatment and management of patients with sickle cell disease.

Haematological profile and malarial parasitaemia in Nigerian children requiring emergency blood transfusion

BACKGROUND

This study was carried out to determine the haematological profile and malarial parasitaemia of children requiring emergency blood transfusion.

METHODS

This prospective study was carried out from 1st August to 30th of November, 1999 at the Children Emergency Ward (CHEW) of the Obafemi Awolowo University Teaching Hospital (OAUTH) Ile-Ife, Nigeria. All children requiring emergency blood transfusion seen at the CHEW were included in the study. Blood samples were taken on admission for haematocrit, white cell count and differentials, thin and thick blood films. Other data recorded include age, sex, clinical impression on admission.

RESULTS

Four hundred children were admitted into the CHEW during the study period and 173(43%) required emergency blood transfusion. One hundred and forty-five (84%) of the children who required emergency transfusion were below the age of five years. There was no sex predilection. Although, clinical impression of malaria was made either singly or in combination with other diseases in almost all the patients, malaria parasitaemia was confirmed in 86 (50%) of the patients. The mean haematocrit was 0.14 L/L. In 60% of the children, there were mixed microcytic hypochromic and macrocytic red bloodcells.

CONCLUSION

We conclude that severe anaemia requiring emergency blood transfusion is a major cause of morbidity and mortality in under five children. We also confirm that malaria and nutritional deficiencies are the major cause of severe anaemia in Nigerian children. We therefore recommend urgent need for prevention and prompt treatment of malaria in children under the age of five years. We also recommend the need for improvement in the nutritional intake of children under the age of five.

Platelet activation and endothelial cell dysfunction in sickle cell disease is unrelated to reduced antioxidant capacity

Possible pathogenetic processes in sickle cell disease include antioxidants, endothelial and platelet changes, and hypercoagulability. Hypothesizing relationships between these processes, we recruited 47 young adult patients (mean age 19 years) with homozygous sickle cell disease and 40 age-, race- and sex-matched healthy controls and measured plasma markers representative of these processes. We found raised plasma von Willebrand factor (P = 0.001) and intercellular adhesion molecule (P = 0.016, both marking endothelial perturbation, but the latter also marking inflammation), raised soluble P selectin (P = 0.002) (marking platelet activation) and inflammation marker C reactive protein (P = 0.021), but reduced antioxidant capacity (P = 0.002) in patients compared with controls. There was no difference in fibrinogen and there was no significant correlation between any of the indices. Our data suggest that changes in endothelial and platelet function in sickle cell disease are unrelated to reduced antioxidant capacity.

Coagulopathies and arterial stroke

Although hypercoagulable states are most often associated with venous thrombosis, arterial thromboses are reported in protein S, protein C, and antithrombin III deficiencies, factor V Leiden and prothrombin gene mutations, hyperhomocysteinemia, dysfibrinogenemia, plasminogen deficiency, sickle cell disease, and antiphospholipid antibody syndrome.

Beta-globin gene cluster haplotypes and HbF levels are not the only modulators of sickle cell disease in Lebanon

Sickle cell disease (SCD) is an inherited autosomal recessive disorder of the beta-globin chain. Despite the fact that all subjects with SCD have the same single base pair mutation, the severity of the clinical and hematological manifestations is extremely variable. This study examined for the first time in Lebanon the correlation between the clinical manifestation of SCD and the beta-globin gene haplotypes. The haplotypes of 50 patients diagnosed with SCD were determined using polymerase chain reaction amplification of fragments containing nine polymorphic restriction sites around and within the epsilon-Ggamma-Agamma-psibeta-delta-beta-globin gene complex. Most reported haplotypes were found in our population with the Benin haplotype as the most prevalent one. When the patients were divided according to their HbF levels into three groups (Group A: HbF < 5%, Group B: HbF between 5 and 15%, and Group C: HbF > 15%), surprisingly, the highest levels of HbF were associated with the most severe clinical cases. Our findings suggest that fetal hemoglobin levels are important but not the only parameters that affect the severity of the disease. In addition, the high levels of HbF in patients with CAR haplotypes did not seem to ameliorate the severity of symptoms, suggesting that genetic factors other than haplotypes are the major determinants of increased HbF levels in Lebanon.

Linus Pauling's "molecular diseases": between history and memory

In 1949, Linus Pauling and his collaborators published a study in the journal Science entitled "Sickle Cell Anemia, a Molecular Disease." In this now classic study, they showed that hemoglobin from patients suffering from sickle cell anemia has a different electrical charge than hemoglobin from healthy individuals. This result demonstrated for the first time that an abnormal protein could be causally linked to a disease, and that genes determined the structure of proteins. This report made headline news and had a powerful impact on both the biomedical community and the general public. Fifty years later, this study is discussed in almost every medical and biological textbook and has became a favorite example in editorials to illustrate the progress of biomedical research. This article explores the history of Pauling's sickle cell anemia and its subsequent integration in different collective memories, up to the present day. It also discusses the function of the collective memories of Pauling's discovery for contemporary biomedical research.

Membrane transport in sickle cell disease

We have reviewed here a number of membrane transport events in red cells from normal individuals and sickle cell patients which respond to changes in O(2) tension. Some deoxygenation-induced changes in membrane permeability are unique to HbS cells and contribute to their dehydration and subsequent sickling. Polymerization of HbS, or specific oxidant damage (or altered redox potential), is a likely factor underlying the abnormal behavior. The key regulatory sites within the membrane or associated proteins remain uncertain and their identity will form the focus of future research. A model for sickle cell dehydration is presented. Inhibition of these permeability changes represents possible avenues for future chemotherapy to ameliorate the condition.

Fetal hemoglobin in sickle cell disease: relationship to erythrocyte phosphatidylserine exposure and coagulation activation

In sickle cell disease (SCD), loss of erythrocyte membrane phospholipid asymmetry occurs with the exposure of phosphatidylserine (PS), which provides a docking site for coagulation proteins. In vivo sickling/desickling, with resulting red cell membrane changes and microvesicle formation, appears to be one of the factors responsible for PS exposure. We evaluated children with SCD homozygous for sickle hemoglobin (SS disease) and controls (n = 65) and demonstrate that high levels of fetal hemoglobin (assessed as F cells) are associated with decreased microvesicle formation, PS exposure, and thrombin generation. F cells correlated inversely with both microvesicles and PS positivity (P <.000001) in SS disease. Multiple regression analyses using various hematologic parameters as independent variables, and either microvesicles or PS positivity as the dependent variable, showed a strong relationship only with F cells. Additionally, plasma prothrombin fragment F1.2 levels (a marker for thrombin generation) correlated with both PS positivity (P <.001) and F cells (P <.01). An F-cell level of approximately 70% was associated with normal levels of prothrombin fragment F1.2 and with microvesicle formation indistinguishable from control values. We suggest that the use of such surrogate biologic markers in conjunction with F-cell numbers may provide valuable insights into the biology and consequences of in vivo sickling.

Acute sickle cell syndromes in Nigerian adults

The pattern of acute illness was determined in 102 adolescents and adults with sickle cell anaemia who presented to the emergency unit of a Lagos hospital. The patients had a mean age of 20.5 years (SD 13.1) and a male-female ratio of 1.5. The symptoms included fever (72%), fatigue and weakness (59%), anorexia (59%) and pain (57.5%) while major clinical signs were pallor (100%), jaundice (71%) and hepatomegaly (68%). Sixty-eight per cent of patients had sickle cell crises, including one with hemiplegic stroke, 10% with combined anaemia and pain crises, 33% with anaemia crises only and 23.5% with pain crises only. Sixty-three per cent had infection which was malaria in 24.5%, bacterial in 17% and viral in 6%. Of 16 patients with pyrexia of unknown origin, seven responded to treatment with chloroquine and eight to antibiotics. Infection was detected in 50% of the patients with sickle cell crises. The association between anaemia crises and malaria was significant (P < 0.05). Of the eight deaths, seven (88%) had anaemia crises. In contrast to studies conducted two decades ago in the same hospital, the prevalence of anaemia crises now exceeds that of pain crises and malaria now exceeds that of bacterial infection. Severe symptomatic anaemia (anaemia crisis) was more frequently associated with infection (mostly malaria) than was bone pain crisis. The Girdle pain crisis more frequently resulted in a fatal outcome than the uncomplicated bone pain crisis.

Acute chest syndrome in adults with sickle cell disease

STUDY OBJECTIVES

Acute chest syndrome (ACS) is a frequent and potentially severe pulmonary illness in sickle cell disease (SCD). The aim of the study was to report the clinical features and outcome of consecutive ACS episodes in adult patients in a French SCD center. All patients were treated according to an uniform therapeutic protocol applying transfusion only in the more severe clinical form of ACS.

RESULTS

There were 107 consecutive episodes in 77 adult patients (mean age, 29 +/- 7 years; 78% hemoglobin [Hb] SS; 14% Hb SC; and 8% Hb Sbeta + thalassemia) over a 6-year period. Seventy-eight percent of our patients had an associated vaso-occlusive crisis that preceded the chest signs in half of the cases. Comparison between acute and baseline levels showed a statistically significant difference in Hb levels (drop of 1.6 to 2. 25 g/dL depending on Hb genotype), WBC count (increase of 9.2 +/- 8. 3 x 10(9)/L); platelet count (increase of 67 +/- 209 x 10(9)/L); and lactate dehydrogenase values (increase of 358 +/- 775 IU/L) in ACS patients. Hypercapnia was detected in 42% of patients without sign of narcotic abuse. We identified a high percentage of alveolar macrophages containing fat droplets in 31 of 43 (77%) patients who underwent BAL. Bacterial culture findings were almost always negative, but were performed after starting antibiotic therapy that was administered in 96 episodes. Transfusion was required in 50 of 107 ACS events (47%). Five patients died, and all were transfused.

CONCLUSIONS

These results confirm that fat embolism is probably a frequent mechanism of ACS in adult patients. However, fat embolism was not associated with a more severe clinical course, suggesting that bronchoscopy and BAL have little impact on the management of these patients. Restricting transfusion to the most severe ACS cases does not seem to increase the mortality rate.

A comparative study of perception of sickle cell anaemia by married Nigeria rural and urban women

Environmental factors may influence perception of or attitude to chronic disorders. The perception of sickle cell anaemia (SCA by 165 married Nigerian rural and 507 urban women was studied to determine how living in an urban or rural environment may influence perception. None of the subjects had children with SCA. The instrument used for data collection was a structured questionnaire designed to enquire into their knowledge about the cause, precipitating factors for crises, clinical features of SCA and their opinions regarding traditional and modern treatment options for the disorder. As a group, urban women had better knowledge about SCA than rural women probably because their social environment afforded a wider scope for interaction with and information exchange among people. For most respondents, the educational institutions attended the health institutions in the locality and the electronic media were poor sources of information on SCA. The study showed a serious lack of information about important aspects of SCA among rural women. We think the training of primary health care providers as counsellors on SCA, the inclusion of instruction about SCA in the curriculum of schools and sustained outreach programmes on SCA on the electronic media would ensure early education of people in both rural and urban communities and help to improve perception of the disorder.

Sickle cell-like crisis and bone marrow necrosis associated with parvovirus B19 infection and heterozygosity for haemoglobins S and E

In the literature, heterozygosity for haemoglobins S and E is known as a clinically benign condition. Nevertheless, we present a case of double heterozygosity manifesting as an infarctive sickle cell-like crisis with acute chest syndrome and reversible bone marrow necrosis. Importantly, these complications were associated with serologically documented parvovirus B19 infection. Reviewing the literature, this case emphasizes a specific role of parvovirus B19 as a precipitating cause. Furthermore, it demonstrates how important the consideration of haemoglobin disorders can be even outside of the historically known areas.

Rheumatic manifestations of infectious diseases in children

Infectious diseases continue to elicit worldwide attention. Many of these diseases have rheumatic manifestations as an incidental or principal feature. Because this is particularly true in children, rheumatic manifestations of infectious diseases in this population continue to be an area of great importance to rheumatologists. A variety of bacteria, viruses, fungi, and parasitic organisms can give rise to infectious diseases with rheumatic manifestations. A high index of clinical suspicion is frequently necessary for an accurate diagnosis. Prompt diagnosis and early and appropriate therapeutic intervention are usually required for a successful, and frequently curative, outcome. Over the past year, studies have addressed the pathogenetic mechanisms and clinical spectrum of the rheumatic manifestations of infectious diseases in children. There has been particular emphasis on septic arthritis, osteomyelitis, sickle-cell disease, and hepatitis C viral infection. There remains the daunting and unfortunate possibility of large numbers of children developing HIV-associated arthritis.

Molecular diseases and diseased molecules: ontological and epistemological dimensions

In 1949, Linus Pauling and collaborators published in Science a paper provocatively titled: 'Sickle cell anemia, a molecular disease'. What was actually meant by 'molecular disease'? We interpret the concept of molecular disease in the frame of the traditional positions about the nature of diseases, the ontological and the physiological positions. We conclude that the physiological does not give an adequate account of what molecular diseases are. The ontological position, when correctly reinterpreted, leads to an understanding of molecular diseases where the macromolecule is seen as a symptom or as a part of a mechanism leading to the symptoms of the disease. We then show that the concept of molecular disease leads to a particular view of therapy, emphasizing eugenics as a way of eliminating disease. On the individual level, this concept leads to an increased power of diagnosis, and especially predictive diagnosis, but has little therapeutic consequence. Lastly, we examine how this concept of disease unifies two contemporary classifications of diseases, one based on the location of the diseases, the other on the cause of the diseases.

Recognition of sickle cell anemia in skeletal remains of children

The present study discusses in detail the osteological changes associated with sickle cell anemia in children and their importance in differential diagnosis. Posterior calcaneal and specific articular surface disruptive metacarpal lesions are diagnostic for sickle cell anemia. Calvarial thickening, tibial and femoral cortical bone thickening, and bowing are of more limited utility in differential diagnosis. Granular osteoporosis, pelvic demineralization and rib broadening are nonspecific. Localized calvarial "ballooning," previously not described, may have diagnostic significance. Bone marrow hyperplastic response (porotic hyperostosis) in sickle cell anemia produces minimal radiologic changes contrasted with that observed in thalassemia and blood loss/hemolytic phenomenon. Two other issues, the osteological criteria for discriminating among the anemias and the purported relationship between porotic hyperostosis and iron deficiency anemia, are also discussed. There is sufficient information to properly diagnose the four major groups of anemias, and further, to establish that iron deficiency is only indirectly associated with porotic hyperostosis. The hyperproliferative bone marrow response (manifest as porotic hyperostosis) to blood loss or hemolysis exhausts iron stores, resulting in secondary iron deficiency.