Variability of homozygous sickle cell disease: The role of alpha and beta globin chain variation and other factors.

The single base molecular substitution characterizing sickle cell haemoglobin, ß6glu→val, might be expected to result in predictable haematological and clinical features. However, the disease manifests remarkable diversity believed to reflect the interaction with other genetic and environmental factors. Some of the genetic modifiers include the beta globin haplotypes, alpha thalassaemia, factors influencing the persistence of fetal haemoglobin and the effects of the environment are addressed in this review. It is concluded that much of the genetic data present conflicting results. Environmental factors such as climate and infections, and psychological, educational and social support mechanisms also influence expression of the disease. These interactions illustrate how the expression of a 'single gene' disorder may be influenced by a variety of other genetic and environmental factors.

ß-Thalassemia Mutations in Jamaica: Geographic Variation in Small Communities.

Over the last 43 years, surveys of over 200,000 subjects in Jamaica have identified ß-thalassemia (ß-thal) mutations. In most, these genes were detected at birth in patients with sickle cell-ß-thal and so the prevalence and distribution would not be influenced by subsequent clinical course. There were two newborn populations, 100,000 deliveries in the corporate area between 1973-1981 and 84,940 in south and western Jamaica between 2008-2016. A third population, which derived from the Manchester Project in central Jamaica, screened 16,612 secondary school children, aged predominantly 15-19 years, and identified 150 students with the ß-thal trait and 11 with sickle cell [Hb S (HBB: c.20A>T)]- or Hb C (HBB: c.19G>A)-ß-thal. The latter patients may have been subject to symptomatic selection, but this should not have affected those with ß-thal trait. Of the 24 different molecular mutations, ß0-thal genes accounted for 10.0-27.0% of these groups and most common was IVS-II-849 (A>G) (HBB: c.316-2A>G). Of the ß+ mutations, seven subjects had severe genes with low levels of ß chain synthesis but the majority were benign mutations in the promoter region. The -29 (A>G) (HBB: c.-79A>G) mutation dominated in the newborn study in Kingston, similar to experiences in Guadeloupe and African Americans but the -88 (C>T) (HBB: c.-138C>T) mutation was more common among school students in central Jamaica. Caribbean populations are genetically heterogeneous but variations within different parts of Jamaica is of potential importance for prenatal diagnosis and genetic counseling. This information may also be useful among the large Jamaican diaspora.

A Plea for the Newborn Diagnosis of Hb S-Hereditary Persistence of Fetal Hemoglobin.

The gene for hereditary persistence of fetal hemoglobin (HPFH) in the Caribbean is much more common than previously estimated. To avoid labeling persons with the benign syndrome Hb S (HBB: c.20A>T)/HPFH as a disease and wasting scarce resources, parental studies are recommended when newborn screening reveals a pattern consistent with an SS phenotype.

Evolving locally appropriate models of care for indian sickle cell disease.

The sickle cell gene in India represents a separate occurrence of the HbS mutations from those in Africa. Sickle cell disease in India occurs against different genetic and environmental backgrounds from those seen in African patients and there is evidence of clinical differences between the populations. Knowledge of the clinical features of African disease was drawn from the Jamaican Cohort Study, based on prospective follow up of all cases of sickle cell disease detected by the screening of 100,000 consecutive newborns in Kingston, Jamaica, and supplemented by observations from the Cooperative Study of Sickle Cell Disease in the US. Defining the principal causes of early morbidity in African sickle cell disease led to successful interventions including pneumococcal prophylaxis, parental education in the early diagnosis of acute splenic sequestration, and the early detection by trans-cranial Doppler of cerebral vessel stenosis predictive of stroke but their success depended on early diagnosis, ideally at birth. Although reducing mortality among patients with African forms of SS disease, the question remains whether these interventions are appropriate or justified in Indian patients. This dilemma is approached by comparing the available data in African and Indian forms of SS disease seeking to highlight the similarities and differences and to identify the deficiencies in knowledge of Indian disease. These deficiencies could be most readily addressed by cohort studies based on newborn screening and since much of the morbidity of African disease occurs in the first five years of life, these need not be a daunting prospect for Indian health care personnel. Newborn screening programmes for sickle cell disease are already underway in India and appropriate protocols and therapeutic trials could quickly answer many of these questions. Without this knowledge, Indian physicians may continue to use possibly unnecessary and expensive models of care.

Phenotypic variation in sickle cell disease: the role of beta globin haplotype, alpha thalassemia, and fetal hemoglobin in HbSS.

INTRODUCTION: The hematological and clinical features vary markedly between the different genotypes of sickle cell disease. Even within the single genotype of homozygous sickle cell disease (HbSS), there is marked variability that is presumed to result from interacting genetic and environmental factors. AREAS COVERED: The classification of the different genotypes of sickle cell disease with approximate prevalence at birth in different communities and some of the major clinical and hematological differences. This assessment includes three potential genetic factors influencing hematology and clinical outcome in HbSS, the beta globin haplotype, alpha thalassemia, and persistence of fetal hemoglobin (HbF). EXPERT OPINION: The author is a clinician with experience of sickle cell disease primarily in Jamaica but also in Greece, Uganda, Saudi Arabia, and India. It is therefore necessarily an account of clinical data and does not address current debates on molecular mechanisms. Most data derive from Jamaica where efforts have been made to reduce any symptomatic bias by long-term follow-up of patients all over the Island and further reduced by a cohort study based on newborn screening, which has been in operation for over 48 years.

Newborn screening for abnormal haemoglobins in Jamaica: Practical issues in an island programme.

OBJECTIVE: To report the diagnostic challenges of newborn screening for abnormal haemoglobins. SETTING: Cord blood samples from 13 hospitals in southwest Jamaica taken in 2008-2019. METHODS: Blood spots, collected from the umbilical cord, were analysed by high pressure liquid chromatography (HPLC) to reveal phenotypes for HbSS and HbCC, but genotype confirmation may require parental studies or gene sequencing. Such cases that were successfully traced were analysed in this follow-up study. RESULTS: HPLC screening of 121,306 samples detected HbAS in 11,846 (9.8%), HbAC in 4508 (3.7%) and other electrophoretic abnormalities in 1090 babies. Among 101 previously unconfirmed cases, 34/90 (38%) with HPLC evidence of a HbSS phenotype had other genotypes, and 7/11 (64%) with a HbCC phenotype had other genotypes. Syndromes from the interaction of ß thalassaemia occurred in 112 babies (85 with HbS, 27 with HbC) and of genes for hereditary persistence of fetal haemoglobin (HPFH) in 18 (12 with HbS, 6 with HbC). Variants other than HbS and HbC occurred in 270 babies, 16 in combination with either HbS or HbC, and 254 as traits. Most variants are benign even when inherited with HbS, although HbO Arab, HbD Punjab, or Hb Lepore Washington, which occurred in 6 cases, may cause sickle cell disease. CONCLUSIONS: Genes for ß thalassaemia and HPFH are common in western Jamaica and when associated with HbS may present diagnostic challenges in newborns, as HbF and HbA2 have not reached diagnostic levels. Family and DNA studies may be necessary for genotype confirmation.

Hb S-ß-thalassemia: molecular, hematological and clinical comparisons.

Clinical and hematological features are presented for 261 patients with identified ß-thalassemia (ß-thal) mutations. Mutations causing Hb S [ß6(A3)Glu→Val]-ß(0)-thal were IVS-II-849 (A>G) in 44%, frameshift codon (FSC) 6 (-A) in 14%, Hb Monroe [ß30(B12)Arg→Thr] in 14%, and IVS-II-1 (G>A) in 10%. Mutations causing Hb S-ß(+)-thal with 14-25% Hb A (type III) were -29 (A>G) mutation in 60%, -88 (C>T) in 22% and the polyadenylation signal site (polyA) (T>C) mutation in 14%, and in Hb S-ß(+)-thal with 1-7% Hb A (type I), all had the IVS-I-5 (G>C) mutation. Hematologically, only minor differences occurred between the four Hb S-ß(0)-thal mutations, but among the three mutations causing Hb S-ß(+)-thal type III, levels of Hb A(2), Hb F, hemoglobin (Hb), MCV and MCH were highest in the -88 and lowest in the polyA mutations. Clinically, Hb S-ß(0)-thal and Hb S-ß(+)-thal type I were generally severe, and Hb S-ß(+)-thal type III disease with the -88 mutation was milder than that caused by the polyA mutation.

Sickle Cell Disease: Thoughts for India From the Jamaican Cohort Study.

The sickle cell gene in India represents a separate occurrence of the HbS mutation (the Asian haplotype), which has occurred against a genetic background characterised by high levels of fetal haemoglobin and widely varying frequencies of alpha thalassaemia. These features, which tend to inhibit sickling, change the expression of the disease, which, in India, may be further modified by poor nutrition, malaria and other infections, and limited public health resources. Sickle cell disease in Jamaica is predominantly of African origin (the Benin haplotype) and faces some similar challenges. This review assesses similarities and differences between disease expression in the two countries and seeks to explore lessons from Jamaica, which may be relevant to Indian health care. In particular, it addresses common causes of hospital admission as detailed from Indian clinical experience: anemia, bone pain crisis, and infections.

Odisha Revisited: A Personal Account.

In 1986, a paper in the Lancet was the first to collate hematology, molecular findings, and clinical features of homozygous sickle cell (SS) disease in India. The paper came from the group organized by Professor Bimal Kar in Burla Medical College, Sambalpur University, in western Odisha. Although widely quoted, few readers will be aware of the history of this work that is now attached in an informal summary.

One hundred years of sickle cell disease.

The first formal report of sickle cell disease occurred 100 years ago. This review traces the early historical reports, the evolution of understanding of the genetics, the molecular and chemical basis of sickle haemoglobin, and the advances made over the last 30-40 years in improving the management. Newborn screening and close follow-up, especially early in life, has significantly improved survival but these advances require resources and sophisticated infrastructure. In sub-Saharan Africa over 250 000 births annually suggest that these advances are unlikely to be implemented within the foreseeable future. Prevention of the disease where possible, could reduce the numbers of new patients allowing better facilities for the care of others. As the disease results from the inheritance of abnormal haemoglobin genes from both parents, it is eminently preventable. The unanswered question, whether genotype detection and counselling will influence reproductive decisions, is currently being addressed by a project in central Jamaica.

Retained placenta in homozygous sickle cell disease.

OBJECTIVE: To document an increased prevalence of retained placenta in mothers with homozygous sickle cell disease. METHODS: A retrospective review (January 1, 1992, to December 31, 2005) at the University Hospital of the West Indies revealed 174 singleton deliveries in women with sickle cell disease who were matched by delivery date and age 1:1 with 174 mothers with normal hemoglobin phenotype. Cesarean delivery in 62 mothers (36%) with sickle cell and in 41 women with normal hemoglobin (24%) left 112 sickle cell and 133 normal hemoglobin pregnancies with spontaneous deliveries. Retained placenta was defined by an interval of at least 30 minutes. Duration and details of the third stage of delivery were obtained by review of records. Duration of delivery stages was assessed by Kaplan-Meier survival charts and tested using the log rank test. Known risk factors were sought by logistic regression or exact logistic regression when the number of outcomes was small. RESULTS: First-stage duration was similar in maternal genotypes (sickle cell 470 minutes [median] compared with normal hemoglobin 335 minutes [median]), but in sickle cell disease, the second stage was slightly delayed (sickle cell 16 minutes compared with normal hemoglobin 15 minutes) and the third stage (sickle cell 7 minutes compared with normal hemoglobin 6 minutes). Retained placenta occurred in 20 mothers (17.9%) with sickle cell (interval 30-340 minutes) compared with four among the women in the control group (3.0%, 30-107 minutes). Apart from a weak association with combined oxytocin and misoprostol, there were no significant associations with known risk factors or with hematologic indices within sickle cell disease. CONCLUSION: Retained placenta is common among mothers with sickle cell disease, and the lack of association with known risk factors suggests that maternal sickle cell disease may be a risk factor. LEVEL OF EVIDENCE: II.

Albuminuria and renal function in homozygous sickle cell disease: observations from a cohort study.

BACKGROUND: The glomerular filtration rate (GFR) in homozygous sickle cell (SS) disease is supranormal in childhood but falls steeply with age, often culminating in renal failure. The risk factors underlying these observations are unclear. We therefore sought to investigate the relationships between blood pressure, renal hemodynamics, and urinary albumin excretion in subjects with SS disease and matched controls with a normal AA genotype (hereinafter, controls) as a prelude to intervention studies. METHODS: Serum creatinine level, GFR, effective renal plasma flow, blood pressure, and urinary albumin and creatinine excretion rates were measured in Jamaican individuals with SS disease aged 18 to 23 years and in controls followed from birth in a cohort study. RESULTS: Compared with controls, subjects with SS disease showed lower blood pressure and normal or supranormal GFR and effective renal plasma flow. Urinary albumin excretion exceeded 20 microg/min in 26% of subjects with SS disease and correlated positively with GFR and systolic blood pressure and negatively with hematocrit. A higher GFR and increased tubular secretion of creatinine combined to lower serum creatinine levels in patients with SS disease, giving an upper limit of the reference range of 0.90 mg/dL (80 micromol/L) in men and 0.77 mg/dL (68 micromol/L) in women. In addition, creatinine clearance measurements were consistently greater than GFR in subjects with SS disease. CONCLUSIONS: The GFR remained within reference range or elevated in patients with SS disease aged 18 to 23 years. The higher GFR in patients with albuminuria was consistent with the hypothesis that high glomerular flows cause renal damage. Lower serum creatinine levels characterize patients with SS disease, and a revised clinical definition based on serum creatinine level alone is proposed.

Causes of death and early life determinants of survival in homozygous sickle cell disease: The Jamaican cohort study from birth.

Globally, the majority of persons born with sickle cell disease do not have access to hydroxyurea or more expensive interventions. The objectives were to estimate the survival in homozygous sickle cell disease, unbiased by symptomatic selection and to ascertain the causes of death in a pre-hydroxyurea population. The utility of early life biomarkers and genetically determined phenotypes to predict survival was assessed. A cohort study based on neonatal diagnosis was undertaken at the Sickle Cell Unit, a specialist clinic delivering care to persons with sickle cell disease in Jamaica. Screening of 100,000 deliveries detected 315 babies with homozygous sickle cell disease of whom 311 have been followed from birth for periods up to 43 years. Pneumococcal prophylaxis and teaching mothers splenic palpation were important, inexpensive interventions. Anticipatory guidance, routine care and out-patient acute care were provided. Each participant was classified as alive, dead, or defaulted (usually emigration). Causes of death were ascertained from clinical records and/or post-mortem reports. Survival was assessed using the Kaplan-Meier function. Sex-adjusted Cox semi-parametric proportional hazards and Weibull modelling were used to assess the effects on survival of biomarkers. Survival to 40 years was 55.5% (95% CI 48.7% to 61.7%). Acute Chest Syndrome (n = 31) and septicemia (n = 14) were significant causes of death at all ages. Acute splenic sequestration (n = 12) was the most common cause of early deaths. Survival was significantly shorter in those with lower hemoglobin at 1 year, high total nucleated count at 1 year, and a history of dactylitis ever. In these hydroxyurea naïve patients, survival into midlife was common. Causes of death were often age specific and some may be preventable. Early life biomarkers predictive of decreased survival in SS disease identify a patient group likely to benefit from close clinical supervision and potentially high risk therapies.

The Bone Pain Crisis of Sickle Cell Disease and Malaria: Observations from Gujarat, India.

BACKGROUND: Sickle cell disease is a common problem across central India, but its clinical features may differ from that in African populations. There is a need to define the features of sickle cell disease in India, and the current study addresses some features of the bone pain crisis. OBJECTIVES: The objective of the study was to describe the epidemiology of the bone pain crisis of sickle cell disease in Gujarat and explore the relationship with infection by Plasmodium vivax. MATERIALS AND METHODS: This was a prospective review of all admissions in patients with sickle cell disease to a private pediatric institution in Bardoli, Gujarat, in the year 2015. Hemoglobin electrophoresis of all patients was consistent with homozygous sickle cell disease, but family studies indicated that at least seven cases had the severe sickle cell-beta + thalassemia presumed to be the common IVS1-5G>C mutation. Clinical, hematological, and parasitological features were recorded. RESULTS: There were 914 admissions among 654 patients who had between one and seven admissions. The bone pain crisis accounted for 763 (83%) of admissions and increased between July and October coinciding with the monsoon period. Blood smears were examined for malarial parasites in 811 admissions and were positive for P. vivax in 73% patients. There was no evidence that P. vivax infections varied with the cause of admission or increased during the monsoon period. CONCLUSIONS: There was a high prevalence of P. vivax infection in hospital admissions of sickle cell patients, but the data did not support an etiological role in the bone pain crisis. A trial of malarial prophylaxis might determine its effect on the clinical features and outcome of sickle cell disease.

Prevention of sickle cell disease: observations on females with the sickle cell trait from the Manchester project, Jamaica.

Screening for haemoglobin genotype was offered to senior school students in Manchester parish in south central Jamaica to test whether this knowledge would influence choice of partner and reduce births with sickle cell disease. Over six academic years, 15,539 students, aged mostly 15-19 years, were screened with voluntary compliance rising from 56 to 92 % over this period. All subjects were given permanent genotype cards and carriers of abnormal genes were offered counselling which explained the reproductive options but avoided recommendations. Prior to screening, all had been offered illustrated lectures on the genetics and clinical features of sickle cell disease. The current study, confined to females with the sickle cell trait, interviewed 763/845 (90.3 %) subjects seeking to assess retention of this knowledge and their response to subsequent boyfriends. Of those interviewed, 42 subjects were excluded (38 emigrated, one died, three received incorrect genotype cards) leaving 721 with complete information. Knowledge of genotype was retained in 95 %, the outcome of future offspring correctly recalled in 91 %, and haemoglobin genotype cards were still possessed by 89 %. A current 'boyfriend' was acknowledged in 403 (56 %) of whom the partner's genotype was known in 88 (74 determined by the project laboratory; 14 by other laboratories) and unknown in 315 (78 %). Offers of free blood tests to all these partners were accepted by only 14 (4 %). Seventeen (2.4 %) were married but the husbands genotype was known in only five (four AA, one AS) of these. Most subjects retain knowledge of their genotype and of its significance for having affected children but the reluctance of partners to be tested was a major obstacle.

Pregnancy in sickle cell-haemoglobin C (SC) disease. A retrospective study of birth size and maternal weight gain.

OBJECTIVE: To assess pregnancy and fetal outcomes in Jamaican subjects with sickle cell-haemoglobin C (SC) disease. STUDY DESIGN: A retrospective chart review over 21 years (1992-2012) of all pregnancies in SC disease and a comparison group matched by gender and date of delivery in mothers with a normal haemoglobin (AA) phenotype at the University Hospital of the West Indies, Jamaica. There were 118 pregnancies in 81 patients with SC disease and 110 pregnancies in 110 in the normal comparison group. Corrections were made for repeat pregnancies from the same mother. Outcome measures included maternal weight at 20, 25, 30, 35 and 38 weeks gestation, maternal pregnancy complications, birth weight, head circumference and crown heel length and were used to analyse possible predictors of birth weight. RESULTS: First antenatal visits occurred later in women with SC disease, who also had lower haemoglobin level and lower systolic blood pressure. The prevalence of pregnancy-induced hypertension, pre-eclampsia, ante-partum or postpartum haemorrhage did not differ between genotypes. Maternal weight gain was significantly lower in SC disease and there was a significantly lower birth weight, head circumference, and gestational age. CONCLUSIONS: Pregnancy in SC disease is generally benign but mothers had lower weight gain and lower birth weight babies, the difference persisting after correction for gestational age.

Incidence and natural history of proliferative sickle cell retinopathy: observations from a cohort study.

OBJECTIVE: To describe the incidence, prevalence, and natural history of proliferative sickle cell retinopathy (PSR). DESIGN: Prospective longitudinal study over 20 years. PARTICIPANTS: Newborn screening of 100000 consecutive deliveries from 1973 to 1981 identified 315 children with homozygous sickle cell (SS) disease and 201 with SS-hemoglobin C (SC) disease. By the age of 5 years, 307 SS patients and 166 SC patients were alive and living in Jamaica and were recruited for this ophthalmic study. METHODS: Description of retinal vascular changes on annual angiography and angioscopy. MAIN OUTCOME MEASURES: Incidence and prevalence of PSR and its behavior on follow-up. Progression of PSR was investigated using the number of eyes affected (none, one, both) and the interval until PSR onset. RESULTS: At last review in January 2000, PSR had developed in 59 patients (14 SS, 45 SC), unilaterally in 36 patients and bilaterally in 23. Incidence increased with age in both genotypes, with crude annual incidence rates of 0.5 cases (95% confidence interval [CI], 0.3-0.8) per 100 SS subjects and 2.5 cases (95% CI, 1.9-3.3) per 100 SC subjects. Prevalence was greater in SC disease, and by the ages of 24 to 26 years, PSR had occurred in 43% subjects with SC disease and in 14% subjects with SS disease. Patients with unilateral PSR had a 16% (11% SS, 17% SC) probability of regressing to no PSR and a 14% (16% SS, 13% SC) probability of progressing to bilateral PSR. Those with bilateral PSR had an 8% (8% SS, 8% SC) probability of regressing to unilateral PSR and a 1% (0 SS, 2% SC) probability of regressing to a PSR-free state. Irretrievable visual loss occurred in only 1 of 82 PSR-affected eyes, and 1 required detachment surgery and recovered normal visual acuity. CONCLUSIONS: Longitudinal observations over 20 years in a cohort of patients followed from birth confirms a greater incidence and severity of PSR in SC disease, and shows that spontaneous regression occurred in 32% of PSR-affected eyes. Permanent visual loss was uncommon in subjects observed up to the age of 26 years.

Leg ulceration in sickle cell disease: medieval medicine in a modern world.

Leg ulceration is now recognized as an important complication of sickle cell disease, especially of the SS genotype. Since there is no convincing evidence of delayed healing of operation scars or of wounds elsewhere in the body, it must be concluded that factors specific to the lower leg render patients prone to delayed healing at this site. Many lesions are traumatic in origin and since there is considerable variation in healing rates among the normal population, it is useful to define chronic leg ulceration on the basis of a minimal duration, which in Jamaican studies has required at least 3 months and sometimes 6 months before healing. This minimal duration avoids the difficulties of interpreting the significance of briefer lesions since the moment of final healing may be poorly defined (patients may conclude that a scab represents healing whereas small lesions persist beneath) and often goes undocumented as patients may not report and medical attendants may not enquire, the date of final healing.