Clinical implications of sickle-cell trait and glucose-6-phosphate dehydrogenase deficiency in hospitalized black male patients

Sickle-Cell Trait and Atopic and Inflammatory Disease in Children

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

Effectiveness of preoperative screening for sickle cell disease in a population with a newborn screening program: a cohort study

PURPOSE

Published clinical practice guidelines recommend that all patients from ethnic groups with a high prevalence of sickle cell disease (SCD) undergo preoperative screening for this hemoglobinopathy. Newborn Screening Ontario initiated a universal sickle hemoglobinopathy screening program in 2006 as part of its regional newborn screening program. The primary objective of this study was to determine the effectiveness of selective preoperative screening for SCD based on at-risk ethnicity in Ontario, a region that has a universal newborn sickle hemoglobinopathy screening program.

METHODS

The hematology laboratory database at our hospital was searched to identify all children who underwent preoperative sickle cell screening in the 42-month period starting in November 2006 (when the newborn sickle hemoglobinopathy screening program was introduced) and ending in April 2010. Medical records of all children testing positive on hemoglobin analysis were reviewed to determine perioperative outcomes.

RESULTS

Our search strategy identified 710 children who were born after the introduction of newborn screening and who underwent preoperative screening. Thirty-five of these children had abnormal sickle solubility tests - one (0.14%) was a new diagnosis (not identified by newborn screening), one had been diagnosed previously, and 33 (4.65%) were identified as having sickle cell trait. Sixty children had more than one preoperative screening test performed (range, 2-4). Six of the 35 children with abnormal sickle solubility results underwent repeated testing.

CONCLUSIONS

Preoperative screening based on at-risk ethnicity alone is an ineffective method of identifying additional children with SCD in Ontario, a population with universal newborn sickle hemoglobinopathy screening. In an effort to avoid unnecessary repeat testing, we propose an algorithm to help physicians decide whether to initiate preoperative sickle cell screening for children.

A review of clinical profile in sickle cell traits

Sickle cell trait is not usually regarded as a disease state because it has complications that are either uncommon or mild. Nevertheless, under unusual circumstances, serious morbidity or mortality can result from complications related to polymerization of deoxy-hemoglobin S. A previous study was earlier conducted to study Sickle cell traits and it revealed that there was enhanced lipid per oxidation along with imbalance in the pro-oxidant and antioxidant status in patients with sickle cell anaemia. Moreover, sickle cell traits present with varied problems including increased urinary tract infection in women, gross hematuria, complications of hyphema, splenic infarction with altitude hypoxia or exercise, life-threatening complications of exercise etc. Renal medullary carcinoma in the young, early onset of end stage renal, as well as disease from autosomal dominant polycystic kidney disease are other well-known occurrences in sickle cell traits. In view of the above facts, this article aims to review the literature to analyze the health status in sickle cell traits.

Framing the research agenda for sickle cell trait: building on the current understanding of clinical events and their potential implications

Sickle Cell Trait (HbAS), the heterozygous state for the sickle hemoglobin beta globin gene is carried by as many as 100 million individuals including up to 25% of the population in some regions of the world (World Health Organization, Provisional agenda item 4.8, EB117/34 (22 December 2005) or World Health Organization, Provisional agenda item 11.4 (24 April 2006)). Persons with HbAS have some resistance to falciparum malaria infection in early childhood (Piel FB, Patil AP, Howes RE, et al., Nat Commun 2010;1104:1-7 and Aidoo M, Terlouw DJ, Kolczak M, et al., Lancet 2002;359:1311-1312) and as a result individuals with HbAS living in malarial endemic regions of Africa have a survival advantage over individuals with HbAA. Reports from the US emphasize possible health risks for individuals with HbAS including increased incidence of renal failure and malignancy, thromboembolic disorders, splenic infarction as a high altitude complication, and exercise-related sudden death. The National Heart, Lung, and Blood Institute, National Institutes of Health convened a workshop in Bethesda, Maryland on June 3-4, 2010, Framing the Research Agenda for Sickle Cell Trait, to review the clinical manifestations of HbAS, discuss the exercise-related sudden death reports in HbAS, and examine the public health, societal, and ethical implications of policies regarding HbAS. The goal of the workshop was to identify potential research questions to address knowledge gaps.

Screening U.S. college athletes for their sickle cell disease carrier status

There are many issues surrounding the screening of collegiate athletes for their sickle cell disease carrier status (or sickle cell trait), a genetic condition. This paper summarizes the establishment of expert advice given to the Secretary's Advisory Committee on Heritable Disorders in Newborns and Children (SACHDNC) on the issue. The SACHDNC has developed a report to advise the Secretary of the USDHHS about the 2010 rule of the National Collegiate Athletic Association (NCAA) requiring testing for sickle cell trait in all incoming Division I student athletes. The SACHDNC does not support the NCAA's rule to screen collegiate athletes for sickle cell trait.

Livedoid vasculopathy associated with sickle cell trait: significant improvement on aspirin treatment

Livedoid vasculopathy (LV) is a chronic, recurrent, painful cutaneous disease manifesting as longstanding distal lower extremity ulcers that scar leaving stellate atrophic lesions known as 'atrophie blanche'. A significant number of cases have been associated with thrombophilic abnormalities. In this study, we describe, to the best of our knowledge, the first report of LV only associated with sickle cell trait with significant improvement on aspirin.

Sickle cell trait is not independently associated with susceptibility to end-stage renal disease in African Americans

Conflicting reports exist as to whether sickle cell trait is a risk factor for the progression of nephropathy. In order to determine whether African Americans with sickle cell trait are at increased risk for kidney disease, we assessed the genetic association between sickle cell trait and end-stage renal disease (ESRD). Hemoglobin S, non-muscle myosin heavy chain 9 (MYH9), and apolipoprotein L1 (APOL1) risk variants were genotyped in 3258 unrelated African Americans: 1085 with non-diabetic ESRD, 996 with type 2 diabetes-associated ESRD, and 1177 controls. Since APOL1 is strongly associated with ESRD in African Americans, interactions between APOL1 and MYH9 risk variants and hemoglobin S were assessed using case-only and case-control centered two-way logistic regression interaction analyses. The sickle cell trait genotype frequencies were 8.7% in non-diabetic ESRD, 7.1% in type 2 diabetes-ESRD, and 7.2% in controls. There was no age-, gender-, and admixture-adjusted significance for sickle cell trait association with non-diabetic ESRD (odds ratio 1.16); type 2 diabetes-ESRD (odds ratio 1.01); or all-cause ESRD (combined non-diabetic and type 2 diabetic-ESRD patients compared to the controls; odds ratio 1.05) in dominant models. In addition, no evidence of APOL1 or MYH9 interactions with sickle cell trait was detected. Hence, sickle cell trait is not associated with diabetic or non-diabetic ESRD in a large sample of African Americans.

Sickle cell considerations in athletes

This article highlights the exertional-sickling collapse syndrome in athletes with sickle cell trait (SCT). It covers all aspects of this syndrome, including pathophysiology, new research on microcirculatory changes, clinical features, differential diagnosis, prevention, and treatment. Also covered in this article are other clinical concerns for athletes with SCT, including lumbar myonecrosis, splenic infarction, hematuria, hyposthenuria, and venous thromboembolism. The final section offers practical points on athletes with sickling hemoglobinopathies more serious than SCT.

Sickle cell trait, hemoglobin C trait, and invasive pneumococcal disease

BACKGROUND

The cause of historically higher rates of invasive pneumococcal disease among blacks than whites has remained unknown. We tested the hypothesis that sickle cell trait or hemoglobin C trait is an independent risk factor for invasive pneumococcal disease.

METHOD

Eligible children were born in Tennessee (1996-2003), had a newborn screen, enrolled in TennCare aged <1 year, and resided in a Tennessee county with laboratory-confirmed, pneumococcal surveillance. Race/ethnicity was ascertained from birth certificates. Children were followed through 2005 until loss of enrollment, pneumococcal disease episode, fifth birthday, or death. We calculated incidence rates by race/ethnicity and hemoglobin type before and after pneumococcal conjugate vaccine (PCV7) introduction. Poisson regression analyses compared invasive pneumococcal disease rates among blacks with sickle cell trait or hemoglobin C trait with whites and blacks with normal hemoglobin, controlling for age, gender, time (pre-PCV7, transition year, or post-PCV7) and high-risk conditions (eg, heart disease).

RESULTS

Over 10 years, 415 invasive pneumococcal disease episodes occurred during 451,594 observed child-years. Before PCV7 introduction, disease rates/100,000 child-years were 2941 for blacks with sickle cell disease, 258 for blacks with sickle cell trait or hemoglobin C trait and 188, 172, and 125 for blacks, whites, and Hispanics with normal hemoglobin. Post-PCV7, rates declined for all groups. Blacks with sickle cell trait or hemoglobin C trait had 77% (95% CI = 22-155) and 42% (95% CI = 1-100) higher rates than whites and blacks with normal hemoglobin.

CONCLUSION

Black children with sickle cell trait or hemoglobin C trait have an increased risk of invasive pneumococcal disease.

High prevalence of sickle cell trait in African Americans with ESRD

Sickle cell trait (HbAS) associates with impaired urinary concentration, hematuria, and renal papillary necrosis, but its prevalence among African Americans with ESRD is unknown. We performed a cross-sectional study reviewing available hemoglobin phenotypes for 188 of 206 adult African-American patients receiving renal replacement therapy in four dialysis units. Results from the state newborn screening program in corresponding counties provided the local population prevalence of sickle trait among African Americans. Compared with the general African-American population, HbAS was twice as common among African Americans with ESRD (15% versus 7%, P < 0.001). Prevalence of hemoglobin C trait (HbAC) was similarly more common (5% versus 2%, P < 0.01). The higher prevalence of HbAS and HbAC in the ESRD population raises the possibility that these hemoglobinopathies contribute to a decline in kidney function, either alone or in conjunction with other known risk factors for renal disease. The potential effect of HbAS on the development and progression of CKD and its effect on the course and management of patients with ESRD deserve further study.

Sickle-cell trait: novel clinical significance

There is a long-standing controversy in the literature as to whether sickle-cell trait (SCT) should be viewed as a benign carrier state or as an intermediate disease phenotype. Because SCT is routinely detected by neonatal screening for sickle-cell disease, it becomes imperative that consensus on this issue be achieved in order to provide the best medical advice to affected individuals. The issue of selective screening in the post-neonatal period was thrust into the limelight recently by the National Collegiate Athletic Association's recommendation that its member colleges and universities test student-athletes to confirm their carrier status if not already known. The stated goal of this recommendation was to prevent exercise-related sudden death in athletes with SCT. We review some of the reported complications of SCT for which new information has emerged, focusing particularly on venous thromboembolism and renal manifestations.

Venous thromboembolism in African-Americans: a literature-based commentary

Among the cardiovascular diseases and after ischemic heart disease and stroke, venous thromboembolism (VTE) is the third leading cause of death in the U.S. (3). Although VTE is seen across most ethnic groups in the U.S. as well as throughout the world, the rate varies. In the U.S., American Indians/Alaskan Natives as well as Asians have been reported to have a significantly lower rate of deep vein thrombosis (DVT) and pulmonary embolism (PE) as compared to blacks and whites. In sharp conrast blacks appear to have much higher rates than whites. Although these rate differences are thought in part by some to be attributable to disparities in diagnosis and care as well as genetics, it nevertheless is important to define as well as to understand the true incidence and impact so that both public health and clinical resources can be maximally utilized. The purpose of this commentary is to review the VTE burden in the U.S. with respect to ethnicity in terms of clinical demographics and genetics with particular emphasis on blacks.

Complications associated with sickle cell trait: a brief narrative review

Sickle cell trait occurs in approximately 300 million people worldwide, with the highest prevalence of approximately 30% to 40% in sub-Saharan Africa. Long considered a benign carrier state with relative protection against severe malaria, sickle cell trait occasionally can be associated with significant morbidity and mortality. Sickle cell trait is exclusively associated with rare but often fatal renal medullary cancer. Current cumulative evidence is convincing for associations with hematuria, renal papillary necrosis, hyposthenuria, splenic infarction, exertional rhabdomyolysis, and exercise-related sudden death. Sickle cell trait is probably associated with complicated hyphema, venous thromboembolic events, fetal loss, neonatal deaths, and preeclampsia, and possibly associated with acute chest syndrome, asymptomatic bacteriuria, and anemia in pregnancy. There is insufficient evidence to suggest an independent association with retinopathy, cholelithiasis, priapism, leg ulcers, liver necrosis, avascular necrosis of the femoral head, and stroke. Despite these associations, the average life span of individuals with sickle cell trait is similar to that of the general population. Nonetheless, given the large number of people with sickle cell trait, it is important that physicians be aware of these associations.

Exchange transfusion for neonatal hyperbilirubinemia with glucose-6-phosphate-deficient blood

Evaluation of: Samanta S, Kumar P, Kishore SS, Garewal G, Narang A: Donor blood glucose-6-phosphate dehydrogenase deficiency reduces the efficacy of exchange transfusion in neonatal hyperbilirubinemia. Pediatrics 123, E96–E100 (2009). Intravascular hemolysis following transfusion with glucose-6-phosphate dehydrogenase (G-6-PD)-deficient blood has been documented, although it is not routine to screen donor blood for this condition prior to exchange transfusion. Samanta et al. studied the effect of exchange transfusion with G-6-PD-deficient donor blood on neonates with moderate hyperbilirubinemia to determine the effectiveness of the exchange, postexchange serum total bilirubin levels, the duration of phototherapy and the need for repeat exchange transfusion. A total of 21 newborns were exchanged with G-6-PD-deficient donor blood and 114 with G-6-PD normal blood. Although the percentage decrease in serum total bilirubin from pre-exchange values immediately following the exchange was similar between the groups, during the postexchange period the percentage decrease became less in those exchanged with G-6-PD-deficient blood. Similarly, the duration of postexchange phototherapy and the number of babies requiring repeat exchange transfusion, were higher in those transfused with G-6-PD-deficient blood. The authors recommend that in areas where G-6-PD deficiency is prevalent, donor blood should be screened for G-6-PD deficiency prior to exchange transfusion use.

Cardiac Surgery and Sickle Cell Disease

Three patients with homozygous sickle cell disease underwent successful open heart surgery for multivalvular lesions. Details of the surgical technique and the necessary precautions are described. Exchange transfusion was implemented in all cases. Crucial issues in cardiac surgical management to avoid or at least minimize vasoocclusive crisis and associated complications are discussed.

Prevalence and Significance of G6PD Deficiency in Patients of an Urban HIV Clinic

The rationale to screen for glucose-6-phosphate dehydrogenase (G6PD) deficiency in HIV-infected individuals is their increased likelihood to receive oxidant drugs and subsequent potential of hemolytic events. However, current guidelines regarding who should be screened are conflicting. The authors examined the prevalence of G6PD deficiency and the frequency of hemolytic events in an urban HIV clinic. They used data from a military database as a comparison. In both cohorts, a relatively high number of black females were found to be G6PD deficient (10% and 13%), which was similar to the rate in men (15% and 12%). No white females were G6PD deficient. The authors identified 8 drug-related hemolytic events in HIV clinic patients. Two patients necessitated blood transfusions; both were triggered by trimethoprim/sulfamethoxazole (TMP/SMX). Although G6PD screening prior to the use of TMP/SMX is not often considered by clinicians, the authors' finding of 2 hemolytic events requiring transfusion suggests this would be beneficial.

(TA)n UDP-glucuronosyltransferase 1A1 promoter polymorphism in Nigerian neonates

Nigerian neonates have a high incidence of bilirubin encephalopathy. Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is prevalent in this population. (TA)7 promoter polymorphism in the gene encoding the bilirubin conjugating enzyme UDP-glucuronosyltransferase 1A1 (UGT1A1) potentiates hyperbilirubinemia in G-6-PD deficient neonates. We studied (TA)n allele frequency to determine, at least in part, its contribution to the frequency and severity of hyperbilirubinemia. DNA was extracted from umbilical cord blood of sequentially born Nigerian neonates and the (TA)n UGT1A1 promoter sequence determined. The (TA)n allele distribution was compared with reported adults of varying African ancestry and Sephardic Jewish neonates. Among 88 Nigerian neonates, (TA)6 and (TA)7 alleles were almost equally distributed (0.46 and 0.43, respectively). Some individuals with (TA)5 and (TA)8 sequences were encountered. Allele distribution was similar to that of the African ancestry population but differed from the Sephardic Jewish newborns, in whom the (TA)6/(TA)7 distribution was 0.65/0.35. Whereas 45% of Nigerian alleles and 50% of African ancestry alleles, respectively, included a (TA)7 or (TA)8 sequence, only 35% of Jewish alleles were (TA)7 (p < 0.001), and no (TA)8 alleles were encountered. The high frequency of (TA)n promoter polymorphism, coupled with G-6-PD deficiency, may contribute to the pathogenesis of extreme neonatal hyperbilirubinemia in Nigeria.

Sickle cell trait and the risk of venous thromboembolism among blacks

People with sickle cell disease have a chronically activated coagulation system and display hemostatic perturbations, but it is unknown whether they experience an increased risk of venous thromboembolism. We conducted a case-control study of venous thromboembolism that included 515 hospitalized black patients and 555 black controls obtained from medical clinics. All subjects were assayed for hemoglobin S and hemoglobin C genotypes. The prevalence of the S allele was 0.070 and 0.032 for case patients and controls, respectively (P < .001). The odds that a patient had sickle cell trait were approximately twice that of a control, indicating that the risk of venous thromboembolism is increased approximately 2-fold among blacks with sickle cell trait compared with those with the wild-type genotype (odds ratio = 1.8 with 95% confidence interval, 1.2-2.9). The odds ratio for pulmonary embolism and sickle cell trait was higher, 3.9 (2.2-6.9). The prevalence of sickle cell disease was also increased among case patients compared with controls. We conclude that sickle cell trait is a risk factor for venous thromboembolism and that the proportion of venous thromboembolism among blacks attributable to the mutation is approximately 7%.

Neonatal hyperbilirubinemia in African American males: the importance of glucose-6-phosphate dehydrogenase deficiency

OBJECTIVE

To perform risk factor analysis for the prediction of hyperbilirubinemia in an African American male neonatal cohort.

STUDY DESIGN

A database of 500 previously published term and near-term African American male neonates was further analyzed to determine the role of risk factors for hyperbilirubinemia. Factors studied included birth weight >/=4.0 kg, gestational age /=75(th) percentile. Hyperbilirubinemia was defined as any bilirubin value >/=95(th) percentile on the hour-of-life-specific bilirubin nomogram.

RESULTS

Forty-three (8.6%) neonates developed hyperbilirubinemia. At 48 +/- 12 hours, median transcutaneous bilirubin was 8.3 mg/dL, 75(th) percentile 10.0 mg/dL, and 95(th) percentile 12.6 mg/dL. Of the risk factors, only exclusive breast-feeding, G-6-PD deficiency and predischarge bilirubin >/=75(th) percentile were significant (Adjusted Odds Ratios [95% Confidence Intervals; CI] 3.15 [1.39-7.14], P = .006; 4.96 [2.28-10.80], P = .001; and 7.47 [3.50-15.94], P < .0001, respectively). G-6-PD-deficient neonates who were also premature and breast-feeding had the highest incidence of hyperbilirubinemia (60%).

CONCLUSIONS

African American male neonates may be at higher risk for hyperbilirubinemia than previously thought. Screening for G-6-PD deficiency and predischarge bilirubin determination may be useful adjuncts in hyperbilirubinemia prediction in these newborns.

Glucose-6-phosphate dehydrogenase activity in term and near-term, male African American neonates

BACKGROUND

We determined values for glucose-6-phosphate dehydrogenase (G-6-PD) activity in African American neonates.

METHODS

G-6-PD activity was measured on umbilical cord blood from term and near-term healthy, male neonates. Neonates were stratified according to the number of neonates for each numerical unit of G-6-PD activity. Corrected end tidal carbon monoxide (ETCOc), a non-invasive index of hemolysis, was performed on each neonate. At least one predischarge transcutaneous bilirubin determination was performed.

RESULTS

Five hundred neonates were studied. Two subpopulations were apparent, with no overlap between the subgroups. Mean value for the 64 (12.8%) infants with the lower values (G-6-PD deficient) was 2.7+/-1.1 U/g Hb, range 0.4-6.6 U/g Hb, while that for the 436 neonates with the higher values (G-6-PD normal) was 21.8+/-2.9 U/g Hb, range 14.5-33.8 U/g Hb. No significant differences in activity were noted between those neonates <37 weeks gestational age and those >37 weeks. Enzyme activity in the lower range in both groups was not related to the development of hyperbilirubinemia. G-6-PD enzyme activity did not correlate with ETCOc values either for the entire cohort or for the individual subsets.

CONCLUSIONS

G-6-PD-deficient neonates formed a separate subgroup from those with normal enzyme activity. The data supplied should facilitate interpretation of G-6-PD test results.

Systematic follow-up and case management of the abnormal newborn screen can improve acceptance of genetic counseling for sickle cell or other hemoglobinopathy trait

PURPOSE

Sickle cell or other hemoglobinopathy trait detected on the newborn screen provides an opportunity for genetic counseling of families at risk of having a child with a major hemoglobinopathy. However, follow-up of hemoglobinopathy trait is often fragmented and acceptance of counseling is low. We describe the results of systematic follow-up and case management of abnormal newborn screen and the effect on acceptance of counseling.

METHODS

From July 1997 to June 2002, families of a newborn with hemoglobinopathy trait were notified by mail. In April 2003, an intensive trait follow-up protocol including letters, telephone calls, educational videos, and genetic counseling was implemented. Demographic information and follow-up activity were documented and tracked using an electronic database.

RESULTS

From July 1997 to June 2002, 3095 families were notified by letter of a newborn with hemoglobinopathy trait and were offered genetic counseling. Of these, 165 (5.3%) received counseling by telephone and 60 (2%) underwent extended family testing. From April to December 2003, 694 families with a newborn with hemoglobinopathy trait were notified by mail. Of these, 362 (52%) families were reached by telephone. Of those contacted by telephone, 92% received genetic counseling via telephone, 57% were interested in family testing, and 12% scheduled an appointment. Additionally, 27% of families were mailed an educational video. Among those declining extended family testing, 26% preferred to consult their pediatrician.

CONCLUSIONS

Systematic follow-up and case management of abnormal newborn screen can improve the acceptance of genetic counseling.

Erythrocyte sickling during exercise and thermal stress

OBJECTIVE

To examine effects of exercise in the heat and fluid intake on erythrocyte sickling and neutrophil activation in carriers of sickle cell trait (HbAS).

DESIGN, SETTING, AND PARTICIPANTS

Six African American men (2 HbAS; 42% HbS, 4 HbAA; 20.7 +/- 0.8 years; 87.4 +/- 9.6 kg) participated in 2 randomized sessions (separate days) each consisting of 45 minutes of brisk walking (treadmill) in a hot (33 degrees C) environment.

INTERVENTION

Subjects consumed no fluids or fluid for 3 hours prior to (ad libitum) and during (1.02 L) testing.

MAIN OUTCOME MEASUREMENTS

Core temperature, heart rate, and perceived exertion were measured. Forearm venous blood was analyzed for percent erythrocyte sickling and plasma myeloperoxidase.

RESULTS

Time-averaged heart rate (126.6 +/- 5.7 vs. 146.7 +/- 5.9 bpm; P = 0.02) and core temperature (37.6 +/- 0.1 vs. 38.1 +/- 0.1 degrees C; P < 0.05) responses were lower during fluid versus no fluid, with no statistically significant difference in perceived exertion (12.3 +/- 0.5 vs. 13.6 +/- 0.4; P = 0.06). Erythrocyte sickling progressively increased (to 3.5%-5.5%) for HbAS carriers during no fluid exercise only. No sickling was detected in HbAA subjects. Plasma myeloperoxidase responses to exercise were greater (P = 0.03) in HbAS versus HbAA.

CONCLUSIONS

Fluid ingestion at a rate sufficient to offset a body weight deficit can effectively reduce erythrocyte sickling during exercise in the heat.

Glucose-6-phosphate dehydrogenase deficiency: a hidden risk for kernicterus

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, a commonly occurring enzymatic defect, is an important risk factor in the pathogenesis of severe neonatal hyperbilirubinemia. Many of the recently reported cases of kernicterus, even in countries with a low overall incidence of the G-6-PD deficiency such as the United States and Canada, have been found to be enzyme deficient. In many cases the hyperbilirubinemia may be due to acute hemolysis precipitated by exposure to an identifiable chemical trigger, or to infection. In other cases the hemolysis may be mild, the hyperbilirubinemia being due to diminished bilirubin conjugation. An interaction between G-6-PD deficiency and promoter polymorphism for the gene encoding the bilirubin conjugating enzyme, UDP-glucuronosyltranferase 1A1, associated with Gilbert syndrome, has been implicated in the pathogenesis of hyperbilirubinemia. Neonates whose families originated in areas at high risk for G-6-PD deficiency should be vigilantly observed for jaundice. Phototherapy is the mainstay of treatment, with exchange transfusion being performed in those unresponsive to phototherapy. A high degree of physician awareness is essential in the identification and follow-up of these high-risk neonates.

Hyperbilirubinemia among African American, glucose-6-phosphate dehydrogenase-deficient neonates

BACKGROUND

Although glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is prevalent in African Americans, their risk of associated neonatal hyperbilirubinemia has not been prospectively studied.

OBJECTIVE

To compare hemolysis and the risk of hyperbilirubinemia among African American, G-6-PD-deficient neonates (study group) and G-6-PD-normal control subjects.

METHODS

Consecutive, healthy, term and near-term, male neonates born to African American mothers comprised the patient cohort. G-6-PD testing was performed with umbilical cord blood samples. Routine management included measurement of the end tidal carbon monoxide level corrected for ambient carbon monoxide level (ETCOc) within 4 hours after delivery (assessment of hemolysis), > or =1 predischarge bilirubin determination, and additional bilirubin testing as clinically indicated. Indications for phototherapy were identical for study patients and control subjects. Neonates were monitored for the first 1 week of life. ETCOc results, the incidence of hyperbilirubinemia (defined as a transcutaneous or plasma total bilirubin concentration of > or =95th percentile for the hour of life), and the need for phototherapy were compared between the G-6-PD-deficient and G-6-PD-normal groups.

RESULTS

Five hundred male patients were enrolled, of whom 64 (12.8%) were G-6-PD-deficient. ETCOc values (median and interquartile range) were higher among G-6-PD-deficient neonates than among control neonates (2.4 ppm [2.0-2.9 ppm] vs 2.1 ppm [1.7-2.5 ppm]). More G-6-PD-deficient neonates developed hyperbilirubinemia than did control subjects (14 of 64, 21.9%, vs 29 of 436, 6.7%; relative risk: 3.27; 95% confidence interval: 1.83-5.86), whereas 13 (20.3%) met the criteria for phototherapy, compared with 25 control subjects (5.7%) (relative risk: 3.53; 95% confidence interval: 1.91-6.56). No cases of kernicterus were observed.

CONCLUSIONS

Within the African American neonatal population, there is a subgroup of G-6-PD-deficient infants with elevated rates of hemolysis, a higher incidence of hyperbilirubinemia, and a greater requirement for phototherapy, compared with G-6-PD-normal control subjects. These newborns should be monitored vigilantly for the development of hyperbilirubinemia.

IDH1 gene transcription is sterol regulated and activated by SREBP-1a and SREBP-2 in human hepatoma HepG2 cells: evidence that IDH1 may regulate lipogenesis in hepatic cells

The mRNA level for cytosolic NADP-dependent isocitrate dehydrogenase (IDH1) increases 2.3-fold, and enzyme activity of NADP-isocitrate dehydrogenase (IDH) 63%, in sterol-deprived HepG2 cells. The mRNA levels of the NADP- and NAD-dependent mitochondrial enzymes show limited or lack of regulation under the same conditions. Nucleotide sequences that are required, and sufficient, for the sterol regulation of transcription are located within a 67 bp region of an IDH1-secreted alkaline phosphatase promoter-reporter gene. The IDH1 promoter is fully activated by the expression of SREBP-1a in the cells and, to a lesser degree, by that of SREBP-2. A 5'-end truncation of 23 bp containing a CAAT and a GC-Box results in 6.5% residual activity. The promoter region involved in the activation by the sterol regulatory element binding proteins (SREBPs) is located at nucleotides -44 to -25. Mutagenesis analysis identified within this region the IDH1-SRE sequence element GTGGGCTGAG, which binds the SREBPs. Similar to the promoter activation, electrophoretic mobility shifts of probes containing the IDH1-SRE element exhibit preferential binding to SREBP-1a, as compared with SREBP-2. These results indicate that IDH1 activity is coordinately regulated with the cholesterol and fatty acid biosynthetic pathways and suggest that it is the source for the cytosolic NADPH required by these pathways.

Prospective brain imaging evaluation of children with sickle cell trait: initial observations

PURPOSE

To determine whether sickle cell trait (hemoglobin AS) is associated with abnormalities in the brain of asymptomatic children.

MATERIALS AND METHODS

Magnetic resonance (MR) imaging and MR angiography were performed prospectively in 26 siblings (eight girls, 18 boys; mean age, 10.5 years) of patients with sickle cell disease. Two neuroradiologists, blinded as to whether a child had hemoglobin AS or AA, reviewed images obtained in siblings. With MR imaging, lacunae, loss of white matter volume, encephalomalacia, or leukoencephalopathy was identified. With MR angiography, arterial stenosis, occlusion, or tortuosity was identified. Images with definite or possible abnormalities were mixed with randomly selected images and were referred to a third neuroradiologist for a completely blinded review. In cases in which all neuroradiologists concurred, a score was assigned that indicated the sibling had an abnormality. MR angiographic findings were assigned a score for tortuosity with a new quantitative scale.

RESULTS

Among 26 siblings screened, 21 children had sickle cell trait. Among these 21 children, two had mild abnormalities at MR imaging (sample prevalence rate, 10% [95% CI: 1%, 29%]), and four had arterial tortuosity (sample prevalence rate, 19% [95% CI: 5%, 42%]). When children with sickle cell trait were compared with 31 control subjects without the trait, arterial tortuosity was significantly more common in children with sickle cell trait (P =.014). Among children with sickle cell trait, percentage of hemoglobin S was significantly greater in children who had tortuosity than percentage of hemoglobin S in children who had normal blood vessels at MR angiography (P <.03).

CONCLUSION

Findings suggest that greater percentage of hemoglobin S is associated with mild vasculopathy. This vasculopathy may explain some of the excess risk of stroke among African Americans.

Anemia and the liver. Hepatobiliary manifestations of anemia

Many types of hemolytic anemia may be associated with liver disease. Liver injury can be caused by the adherence of deformed or hemolyzed erythrocyses to hepatic vascular endothelium. Adhesion of large numbers of hemolyzed red blood cells to hepatic macrophages, or occlusion of hepatic sinusoids by fragmented red cells, can also result in injury of the liver. Thrombosis of the hepatic or portal vein is associated with some types of hemolytic anemia, and can cause severe liner injury. These are some examples of hepatic injury that can be caused by hemolytic anemias. This article discusses some aspects of liver disease that is associated with sickle cell anemia, paroxysmal nocturnal hemoglobinuria, glucose-6-phosphate dehydrogenase deficiency, hereditary spherocytosis, and HELLP syndrome.

Anemia

Anemia is an enormous problem worldwide that is worse in the developing countries but by no means lacking in developed countries. Women and children are disproportionately affected. Nutritional anemias, mainly caused by a lack of iron and folate, are largely correctable by dietary improvement, but this socioeconomic change may not be readily achieved. The inherited disorders, the hemoglobinopathies and thalassemias, in their heterozygous forms are beneficial to the affected populations. Prevention of the homozygous forms and the serious diseases that result can only be addressed by education. These conditions are seen in all types of medical practice ranging from neonatology to geriatrics and public health and are an ongoing concern to all physicians.

Sports haematology

While the crucial role of haemoglobin in aerobic exercise has been well accepted, there is still a great deal of controversy about the optimal haematological parameters in the athletic population. The initial part of this review will examine the question of anaemia in athletes. The most common finding in athletes is a dilutional pseudoanaemia that is caused by a plasma volume expansion, rather than an actual blood loss. It is not a pathological state and normalises with training cessation in 3 to 5 days. This entity should be distinguished from conditions associated with lowered blood counts, such as intravascular haemolysis or iron deficiency anaemia. The evaluation of true anaemia states in the athlete must take into account not only blood losses secondary to exercise, such as foot strike haemolysis or iron losses through sweat, but non-athletic causes as well. Depending on the age and sex of the athlete, consideration must be given to evaluation of the gastrointestinal or genitourinary systems for blood loss. Finally, a comprehensive nutritional history must be taken, as athletes, especially women, are frequently not consuming adequate dietary iron. The second section of the paper will deal with the very contentious issue of sickle cell trait. While there have been studies demonstrating an increased risk of sudden death in people with sickle cell trait, it is still quite rare and should not be used as a restriction to activity. Further, studies have demonstrated that patients with sickle cell trait have an exercise capacity that is probably normal or near normal. However, in the cases of sudden death, it has been secondary to rhabdomyolysis occurring among sickle cell trait athletes performing at intense exertion under hot conditions, soon after arriving at altitude. The recommendations are that athletes with sickle cell trait adhere to compliance with the general guidelines for fluid replacement and acclimatisation to hot conditions and altitude. The final section of the paper examines the issue of haematological manipulation for the purposes of ergogenic improvement. Although experiments with blood doping revealed improvements in running time to exhaustion and maximal oxygen uptake, the introduction of recombinant erythropoietin has rendered blood doping little more than a historical footnote. However, the improvements in performance are not without risk, and the use of exogenous erythropoietin has the potential for increased viscosity of the blood and thrombosis with potentially fatal results. Until a definitive test is developed for detection of exogenous erythropoietin, it will continue to be a part of elite athletics.

Cancer as a marker of genetic medical disease: an unusual case of medullary carcinoma of the kidney

Medullary carcinoma is a recently recognized tumor of the kidney with distinctive microscopic features; the most notable are diffuse and glandular growth patterns, inflammatory infiltrates, and rhabdoid/plasmacytoid cells. It is a clinically aggressive tumor that occurs in relatively young patients. Moreover, this tumor shows a peculiar clinical association: it occurs in patients with sickle cell hemoglobinopathy. The case presented is that of a 37-year-old black woman with a history of bronchial asthma who died suddenly. Autopsy showed a 4-cm renal mass with extension to the inferior vena cava and metastases to the liver. Histologic evaluation showed the characteristic findings of medullary carcinoma of the kidney. This diagnosis prompted the investigation and subsequent detection of sickle cell trait in the deceased, alerting the family to the genetic nature of her illness. This case is the first report of this entity since the original described series of patients and shows the unique nature of this cancer as a marker of a genetic medical disease.

A new lease of life for an old enzyme

We review here some recent data about glucose-6-phosphate dehydrogenase (G6PD), the first and key regulatory enzyme of the pentose phosphate pathway. New evidence has been presented to suggest that malaria is a selective agent for G6PD deficiency, which is the most common enzymopathy in man, and that G6PD deficiency, generally considered to be a mild and benign condition, is significantly disadvantageous in certain environmental conditions. At the molecular level, the enzyme structure has recently been elucidated and mechanisms regulating G6PD gene expression have been determined. A G6PD knock-out mutation introduced in mouse cells makes them exquisitely sensitive to oxidative stress, indicating that this ubiquitous metabolic enzyme has a major role in the defence against oxidative stress, even in eukaryotic nucleated cells, which have several alternative routes for providing the same protection. Because of the high prevalence of G6PD deficiency in many populations, it is expected that these findings will prompt further studies to ascertain the putative role of G6PD deficiency in conditions such as carcinogenesis and ageing.

Hemolysis after acetaminophen overdose in a patient with glucose-6-phosphate dehydrogenase deficiency

CASE REPORT

A sixteen year-old-male with a history of glucose-6-phosphate dehydrogenase deficiency ingested an unknown amount of acetaminophen and presented to an emergency department 7.5 h later. He was afebrile. His serum acetaminophen level was 184 micrograms/mL, and his urine toxicologic screen was otherwise negative. Vomiting led to enrollment in a experimental protocol of intravenous N-acetylcysteine. He developed no evidence of subsequent chemical hepatitis but did develop a significant Coomb's negative hemolytic anemia. Hemoglobin on presentation was 14 g/dL and reached a nadir of 9.4 g/dL on admission day 4.

CONCLUSION

Patients with glucose-6-phosphate dehydrogenase deficiency who overdose with acetaminophen should be monitored for the possible development of subsequent drug-induced hemolysis.

Natural selection of hemi- and heterozygotes for G6PD deficiency in Africa by resistance to severe malaria

Glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common enzymopathy of humans, affects over 400 million people. The geographical correlation of its distribution with the historical endemicity of malaria suggests that this disorder has risen in frequency through natural selection by malaria. However, attempts to confirm that G6PD deficiency is protective in case-control studies of malaria have yielded conflicting results. Hence, for this X-linked disorder, it is unclear whether both male hemizygotes and female heterozygotes are protected or, as frequently suggested, only females. Furthermore, how much protection may be afforded is unknown. Here we report that, in two large case-control studies of over 2,000 African children, the common African form of G6PD deficiency (G6PD A-) is associated with a 46-58% reduction in risk of severe malaria for both female heterozygotes and male hemizygotes. A mathematical model incorporating the measured selective advantage against malaria suggests that a counterbalancing selective disadvantage, associated with this enzyme deficiency, has retarded its rise in frequency in malaria-endemic regions. Although G6PD deficiency is now regarded as a generally benign disorder, in earlier environmental conditions it could have been significantly disadvantageous.

The pathophysiology of the sickle hemoglobinopathies and implications for perioperative management

Patients with sickle hemoglobinopathies are at risk for unique postoperative complications and increased mortality. Understanding the pathophysiology of these disorders is important for safe perioperative management. Because there is no animal model for sickle cell disease, understanding has progressed through in vitro studies and clinical observations. This review describes the clinical manifestations of the sickle hemoglobinopathies with special emphasis on current knowledge of pathophysiology. It also discusses issues of preoperative screening, transfusion, and postoperative care.

Hemolytic anemia following succimer administration in a glucose-6-phosphate dehydrogenase deficient patient

Because of its favorable side effects profile, the oral chelating agent dimercaptosuccinic acid is often used for treatment of lead intoxication. We report a case of a 45-year-old black male with glucose-6-phosphate dehydrogenase deficiency and a 17 year history of occupational lead exposure who developed hemolysis during treatment with dimercaptosuccinic acid for symptomatic lead intoxication.