Benign obstetric history in women with sickle-cell anaemia associated with -thalassaemia

Alpha thalassemia among sickle cell anaemia patients in Kampala, Uganda

BACKGROUND

Sickle cell anaemia is prevalent in sub Saharan Africa. While α+-thalassaemia is known to modulate sickle cell anaemia, its magnitude and significance in Uganda have hitherto not been described.

OBJECTIVES

To determine the prevalence of α+thalassaemia among sickle cell anaemia patients in Mulago Hospital and to describe the clinical and laboratory findings in these patients.

METHODS

A cross sectional study was carried out on patients with sickle cell anaemia in Kampala. Dried blood spots were used to analyze for the deletional α+ thalassaemia using multiplex polymerase chain reaction.

RESULTS

Of the 142 patients with sickle cell anaemia, 110 (77.5%) had the αα+thalassaemia deletion. The gene frequency of (-α) was 0.425. Ninety one percent (100/110) of those with α+thalassaemia were heterozygous (αα/α-). Amongst the patients older than 60 months, 15 (83.3%) of those without αα+thalassaemia had significant hepatomegaly of greater than 4 cm compared to 36 (45.6%) of those with α+thalassaemia (p=0.003).

CONCLUSION

The gene frequency of (-α) of 0.425 noted in this study is higher than that reported from many places in Africa. Concurrent alpha thalassemia might be a protective trait against significant hepatomegaly in sickle cell anaemia patients more than 60 months of age at Mulago hospital.

Is Hb A2 elevated in adults with sickle-alpha-thalassemia (beta(S)/beta(S); -alpha/-alpha)?

Thirteen patients with sickle cell anemia (SS) were found to have two alpha gene deletions with a presumptive genotype of beta(S)/beta(S); -alpha/-alpha. Hematological data showed that this group of patients had elevated Hb A2 level. In order to determine whether the elevation of Hb A2 is typical of SS with a two alpha gene deletion or is due to undiagnosed S-beta(O)-thalassemia with a two alpha gene deletion we looked for the presence or absence of beta(O)-thalassemia by molecular techniques. The latter included reverse dot-blot hybridization to rule out a beta-thalassemia mutation, digestion with CvnI endonuclease followed by Southern blotting and hybridization with a beta genomic probe, and, in selected patients, determination of the synthetic alpha/beta ratio. One of the 13 patients had S-beta(O)-thalassemia with a G-->A mutation at IVS-II-1 indicating that her genotype was beta(S)/beta(O) thalassemia; -alpha/-alpha. The remaining 12 patients were homozygous for the sickle gene, had relatively elevated Hb levels, increased Hb A2 values, and Hb F levels similar to those in patients with SS and four or three alpha genes. At the clinical level, the 12 patients with SS and a two alpha gene deletion had increased prevalence of avascular necrosis, retinopathy, and splenomegaly, but decreased prevalence of leg ulcers and cerebrovascular accidents. Together, the data indicate that SS with a two alpha gene deletion (beta(S)/beta(S); -alpha/-alpha) is a unique subset of patients with SS characterised by distinct hematological and clinical features.

The interaction of coexistent alpha-thalassemia and sickle cell anemia: a model for the clinical and cellular results of diminished polymerization?

Review of the studies on the interaction of alpha-thalassemia and sickle cell anemia reveals a consistently beneficial effect on the severity of anemia and the rheologic and cellular properties of sickle cells. The predominantly vaso-occlusive clinical aspects of sickle cell anemia studied are not uniformly benefited by the presence of alpha-thalassemia. These variable results may be related to the detrimental effects of higher hematocrit on whole blood viscosity. The effects of alpha-thalassemia on sickle cell anemia are probably related to a fundamental effect on MCHC and polymerization, although coexistent effects on other properties of sickle cells and the possibility that the MCHC differences may be secondary to sickling effects cannot be excluded. In total, alpha-thalassemia is an imperfect model for the effects of polymerization on the clinical consequences of sickle cell disease. An important inference from the published literature is that the severity of anemia may be a more important determinant of the ultimate clinical consequence of sickle cell anemia, life expectancy, than has previously been appreciated. Although the effect of alpha-thalassemia is an imperfect model for modified polymerization, studies of the phenotypic result of the interaction of these two genotypes will provide further insight into the causes of clinical diversity in sickle cell disease.

Interaction between HBS-beta-o-thalassemia and alpha-thalassemia

We have defined the clinical and laboratory characteristics of a group of patients with HbS-beta o-thalassemia plus alpha-thalassemia, by analysis of erythrocyte indices, hemoglobin A2 and F levels, globin biosynthesis studies and alpha-globin gene mapping. Patients with HbS-beta o + alpha-thalassemia closely resembled individuals with HbS-beta o-thalassemia except for balanced globin synthesis ratios and a lower HbF level. The frequency of painful crises, leg ulceration, aseptic necrosis of bone and acute chest syndrome was similar in HbS-beta o + alpha-thalassemia patients and controls with sickle cell anemia (HbSS), HbSS-alpha-thalassemia and HbS-beta o-thalassemia. These findings are consistent with previous work which failed to show a reduction in the vaso-occlusive severity of sickle cell disease by the coexistence of alpha-thalassemia.

Heterogeneity of sickle-cell anemia based on a profile of hematological variables

Factors that influence the heterogeneity of the disease expression of sickle-cell anemia are not well understood. This study examines the ability of a profile of six hematological variables (HB, HCT, RBC, %Hb F, MCV, and %HBA2) to predict the severity of disease measured on 225 patients ranging from 0.2 to 18 years of age. Four subgroups of patients were identified separately in each sex using cluster analysis techniques. In each sex, mean hemoglobin concentration and percent Hb F increased across the four clusters from 7 to 10 gm/dl and from 7% to 16%, respectively. Mean cell volumes were approximately 90, 80, 90, and 75 in groups 1, 2, 3, and 4, respectively; thus MCV did not increase in an orderly progression along with HB and %Hb F. We studied the distribution of four anthropometric, five physical examination, and seven clinical measures of disease severity among clusters. In each sex, subgroups differed significantly (P less than .05) for percent ever hospitalized for sickle-cell anemia, percent ever transfused, and percent with bone-age delays greater than 1 year. In addition, male clusters differed significantly for percent ever having had pneumonia, priapism, or dactylitis, and females differed significantly for height and weight. %Hb F and its inverse relationship with %HBA2 was more highly associated with the measures of severity than the degree of anemia or MCV. This study establishes the utility of a vector of hematological variables as a predictor of heterogeneity of measures of clinical manifestations among young patients with sickle-cell anemia. The role of alpha-thalassemia and genetic factors that affect Hb F levels were considered as possible explanations for the observed heterogeneity.

The interaction of alpha-thalassemia and homozygous sickle-cell disease

Patients with homozygous sickle-cell disease may be homozygous for alpha-thalassemia 2 (alpha-/alpha-), may be heterozygous for alpha-thalassemia 2 (alpha-/alpha alpha), or may have a normal alpha-globin-gene complement (alpha alpha/alpha alpha). We compared the clinical and hematologic features of 44 patients who had sickle-cell disease and homozygous alpha-thalassemia 2 with those of controls with the two hematologic conditions. The patients with homozygous alpha-thalassemia 2 had significantly higher red-cell counts and levels of hemoglobin and hemoglobin A2, as well as significantly lower hemoglobin F, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, mean corpuscular volume, reticulocyte counts, irreversibly-sickled cell counts, and serum total bilirubin levels, than those with a normal alpha-globin-gene complement. Heterozygotes (alpha-/alpha alpha) had intermediate values. In the group with homozygous alpha-thalassemia 2, fewer patients had episodes of acute chest syndrome and chronic leg ulceration and more patients had splenomegaly, as compared with patients in other two subgroups. These data confirm previous suggestions that alpha-thalassemia inhibits in vivo sickling in homozygous sickle-cell disease and may be an important genetic determinant of its hematologic severity.

Long survival in sickle cell anemia

Ten patients with sickle cell anemia surviving beyond the age of 40 were compared to 11 subjects with sickle cell anemia who died before that age. Hematologic and biochemical data as well as clinical and physical parameters of the two groups were compared. There was no statistically significant difference between the two groups with respect to the degree of anemia, severity of hemolysis, or hemoglobin A2 levels. A statistically significant difference was found between the two groups with respect to fetal hemoglobin, red cell zinc, and secondary sexual characteristics. Although the long survivors had fewer crises per year than the short survivors, the long-term complications such as leg ulcer, congestive heart failure, and aseptic necrosis of the hip were more common in the older patients. Cerebrovascular accidents were the cause of death in 9/11 short survivors and are absent in the long survivors. The alpha/beta chain synthesis ratio was normal in the long-survivor group and alpha gene mapping in five subject in that group revealed the genotype alpha alpha/alpha alpha in four and -alpha/alpha alpha in one. The older patients as a group had higher red cell zinc values. The secondary sexual characteristics were also better developed in the older subjects. The overall significance of zinc status and of a higher HbF on longevity of sickle cell anemia patients remains unknown.

Sickle cell disease in Saudi Arabs in early childhood

Haemoglobin electrophoresis screening of 2341 infants from the oases of eastern Saudi Arabia, performed in an attempt to detect cases early and then to follow up and give better management to patients with sickle cell disease, showed 20% with S-trait and 43 with sickle cell disease (37 HbSS and 6 S-beta(0) thalassaemia). On follow-up from birth (or from 3 months) for a mean of 3 1/2 years there was more morbidity and mortality than in matched Saudi Arab controls, but these rates were lower than for affected black infants in the US or Jamaica. Serial haemoglobin levels were l g/dl lower than for controls; height and weight increases were the same. Mean fetal haemoglobin level was 32% at 4-5 years. Half of a subsample of 23 cases had evidence of coexistent alpha-thalassaemia which appeared to protect against functional asplenia, judged by the presence of Howell-Jolly bodies; however there was no difference in degree of anaemia or clinical course. Early screening is recommended for infants at risk for sickle cell disease, and comprehensive care should be given even if the infant has the less severe type.

Lack of influence of fetal hemoglobin levels or erythrocyte indices on the severity of sickle cell anemia

Persons with sickle cell anemia who have elevated fetal hemoglobin or lowered erythrocyte mean corpuscular volume are reputed to have less severe clinical manifestations and a greater probability of survival. This study examines the relationship between seven clinical indicators of morbidity in sickle cell anemia and seven hematological parameters that were collected from 214 patients. Risks of sickle cell crisis, acute chest syndrome, hospital admissions, cerebrovascular accident, aseptic necrosis, meningitis/septicemia, and death were used as indicators of morbidity. The hematological parameters included percent fetal hemoglobin, absolute fetal hemoglobin, percent hemoglobin A2, hemoglobin concentration, packed cell volume, mean corpuscular volume, and mean corpuscular hemoglobin concentration. Statistical analyses of the data showed no relationship between the hematological parameters and six of the seven clinical indicators of the severity of sickle cell anemia. The only significant finding was an increased risk of stroke in those patients with lower levels of fetal hemoglobin. Therefore, with this exception, there is no predictable relationship between morbidity and mortality in sickle cell anemia and levels of fetal hemoglobin or erythrocyte indices. Thus, the general belief that there is an association between severity of sickle cell anemia and the levels of fetal hemoglobin has not been established.

Hematological and clinical features of sickle cell diseases: a review

The differentiation, hematologic features and clinical manifestations of patients with the various sickling disorders are reviewed. The deficiencies in our current knowledge about the spectrum of the clinical course of patients with these conditions is discussed. The interaction of alpha thalassemia with sickle cell anemia and its possible effect upon the severity of the disease is summarized. The apparent milder disease in certain groups of patients with sickle cell anemia in whom there is an associated elevation of hemoglobin F is contrasted with the controversy surrounding the effects of hemoglobin F levels in the patients of African origin.

Modification of hemoglobin H disease by sickle trait

The rarity of hemoglobin (Hb) H disease in combination with sickle trait may be due in part to the absence of actual Hb H in individuals who, nonetheless, have inherited the deletion of three alpha-globin genes. We describe here a boy with persistent microcytic, hypochromic anemia despite adequate iron stores, who exhibited splenomegaly with a normal reticulocyte count and only rare inclusions in circulating erythrocytes. Starch gel electrophoresis and isoelectric focusing at age 5 yr showed 21% Hb S, persistent Hb Bart's, but no Hb H. Recticulocyte alpha/non-alpha globin chain synthesis ratio was 0.58 at age 5. The mother (Asian) had laboratory evidence of alpha-thalassemia trait and the father (Black) had sickle trait. The nature of alpha-thalassemia in this patient was investigated both by liquid hybridization and by the Southern method of gene mapping, in which DNA is digested with restriction endonucleases and the DNA fragments that contained the alpha-globin structural gene identified by hybridization with complementary DNA. The patient had only one alpha-globin structural gene, located in a DNA fragment shorter than that found in normal or alpha-thalassemia trait individuals, but similar to that present in other patients with Hb H disease. Morphologic studies of bone marrow by light and electron microscopy revealed erythroid hyperplasia with inclusions in polychromatic and orthochromatic erythroblasts, suggesting early precipitation of an unstable hemoglobin. The lack of demonstrable Hb H may be the result of both diminished amounts of beta(A) available for Hb H formation (since one beta-globin gene is beta(S)) and the greater affinity of alpha-chains for beta(A) than beta(S)-globin chains leading to the formation of relatively more Hb A than Hb S. The presence of a beta(S) gene may thus modify the usual clinical expression of Hb H disease.

Sickle cell anemia as a syndrome: a review of diagnostic features

Sickle cell (SS) disease is a complex of various genetic conditions. In some, homozygosity for the beta S gene may be present alone or in combination with the heterozygous or homozygous alpha-thalassemia-2 condition. Such combinations might ameliorate the clinical and hematological condition of the patient. The same may be true for the high levels of Hb F and F-cells observed in many Hb S homozygotes. Howeever, the chemical heterogeneity of Hb F appears not to be related to the clinical status of the Hb S homozygote. Combinations of a Hb S heterozygosity with a heterozygosity for a Hb D-type of variant, for either one of two types of beta-thalassemia, two types of alpha beta- thalassemia, and five types of HPFH are discussed, and data are compared with those obtained for Hb S homozygotes. The use of advanced laboratory procedures and family studies is often necessary for an accurate diagnosis.

Sickle cell anemia and trait in southern India: further studies

Population surveys and family studies among 568 members of nine ethnic groups in southern India identified 15 homozygotes for sickle hemoglobin (HbS)who had mild clinical and hematological manifestations with high levels of fetal hemoglobin (mean=20%, range 8-36%) in a heterogeneous red cell distribution. In one family, the heterozygous mother had a hemoglobin pattern consistent with a form of the heterocellular hereditary persistence of fetal hemoglobin. Sickle cell trait was found in 153(27%) of those studied. Chromatographic quantitation of the hemoglobin fractions in these heterozygotes showed a trimodal distribution of the proportion of HB Sexplicable by a genetic model postulating the presence of genotypes with two (-alpha/-alpha), three (-alpha/alpha alpha) and four (alpha alpha/alpha alpha) active alpha-globin genes. Globin synthesis studies in four heterozygotes believed to have two active alpha-globin genes demonstrated an alpha/non-alpha total activity ratio (0.57) consistent with this model.

On the nature of sickle-cell disease in the Arabian Peninsula

The sickle-cell gene contributes substantially to the presentation of anaemia in certain areas of the Arabian Peninsula. However, the clinical presentation of the homozygous state of Hb S is less severe than that observed in other ethnic groups, such as American negroes. In the present paper, biosynthesis studies performed on reticulocytes from heterozygotes and homozygotes for the Hb S give further indications of the mild nature of sickle-cell disease in Arabia. Comparison of two affected families, from Saudi Arabia and Jordan, showed that clinical manifestation of the disease is mirrored by the biochemical and haematological findings in affected individuals. The results are discussed in terms of the effect of co-existing thalassaemia and/or iron deficiency with Hb S. It is suggested that both genetic and acquired conditions play a role in the clinical features of the disease. The mechanisms responsible for regulation of alpha-chain synthesis by iron (haem) deficiency are discussed.

Sickle cell syndromes. II. The sickle cell anemia-alpha-thalassemia syndrome

Five American black patients, ages 1 to 16 years, with the sickle cell anemia-alpha-thalassemia syndrome are described. Each patient had persistent microcytosis not explained by iron deficiency, and in each family the presence of alpha-thalassemia in combination with sickle cell trait was demonstrated in one of the parents. In one patient, in whom the diagnosis of sickle cell anemia was established at birth, an elevated level of Barts (gamma4) hemoglobin was also found. In these patients levels of alkali-resistant hemoglobin and reticulocyte counts were similar to those of sickle cell anemia patients of comparable age; however, stained smears of their peripheral blood rarely showed the presence of irreversibly sickled cells. No major ameliorative effect of the alpha-thalassemia on the clinical expression of the sickle cell disease of these patients was evident.

Alpha-thalassemia

The current concepts of alpha-thalassemia including incidence, genetics, clinical spectrum and diagnosis are reviewed. Speculation concerning clinical application of the molecular biology of alpha-thalassemia is also presented.