Comparison of haematological features of the beta0 and beta+ thalassaemia traits in Jamaican Negroes

The beta thalassaemia trait in Jamaica

The objective of this study was to review the prevalence and features of the beta thalassaemia trait in Jamaican populations. Screening of 221,306 newborns over the last 46 years has given an indication of the distribution and prevalence of beta thalassaemia genes, and screening of 16,612 senior school students in Manchester parish, central Jamaica, has provided their haematological features. The prevalence of the beta thalassaemia trait predicted from double heterozygotes was 0.8% of 100,000 babies in Kingston, 0.9% of 121,306 newborns in southwest Jamaica, and 0.9% of school students in Manchester. Mild beta+ thalassaemia variants (-88 C>T, -29 A>G, -90 C>T, polyA T>C) accounted for 75% of Kingston newborns, 76% of newborns in southwest Jamaica, and 89% of Manchester students. Severe beta+ thalassaemia variants were uncommon. Betao thalassaemia variants occurred in 43 patients and resulted from 11 different variants of which the IVSII-849 A>G accounted for 25 (58%) subjects. Red cell indices in IVSII-781 C>G did not differ significantly from HbAA, and this is probably a harmless polymorphism rather than a form of beta+ thalassaemia; the removal of 6 cases in school screening had a minimal effect on the frequency of the beta thalassaemia trait. Red cell indices in the beta+ and betao thalassaemia traits followed established patterns, although both were associated with increased HbF levels. The benign nature of beta+ thalassaemia genes in Jamaica means that cases of sickle cell-beta+ thalassaemia are likely to be overlooked, and important clinical questions such as the role of pneumococcal prophylaxis remain to be answered.

Hb S/-Thalassemia in the REDS-III Brazil Sickle Cell Disease Cohort: Clinical, Laboratory and Molecular Characteristics

We described the clinical, laboratory and molecular characteristics of individuals with Hb S (HBB: c.20A>T)/β-thalassemia (Hb S/β-thal) participating in the Recipient Epidemiology and Donor Evaluation Study (REDS-III) Brazil Sickle Cell Disease cohort. HBB gene sequencing was performed to genotype each β-thal mutation. Patients were classified as Hb S/β⁰-thal, Hb S/β⁺-thal-severe or Hb S/β⁺-thal based on prior literature and databases of hemoglobin (Hb) variants. Characteristics of patients with each β-thal mutation were described and the clinical profile of patients grouped into Hb S/β⁰-thal, Hb S/β⁺-thal and Hb S/β⁺-thal-severe were compared. Of the 2793 patients enrolled, 84 (3.0%) had Hb S/β⁰-thal and 83 (3.0%) had Hb S/β⁺-thal; 40/83 (48.2%) patients with Hb S/β⁺-thal had mutations defined as severe. We identified 19 different β-thal mutations, eight Hb S/β⁰-thal, three Hb S/β⁺-thal-severe and eight Hb S/β⁺-thal. The most frequent β⁰ and β⁺ mutations were codon 39 (HBB: c.118C>T) and IVS-I-6 (T>C) (HBB: c.92+6T>C), respectively. Individuals with Hb S/β⁰-thal had a similar clinical and laboratory phenotype when compared to those with Hb S/β⁺-thal-severe. Individuals with Hb S/β⁺-thal-severe had significantly lower total Hb and Hb A levels and higher Hb S, white blood cell (WBC) count, platelets and hemolysis markers when compared to those with Hb S/β⁺-thal. Likewise, individuals with Hb S/β⁺-thal-severe showed a significantly higher occurrence of hospitalizations, vaso-occlusive events (VOE), acute chest syndrome (ACS), splenic sequestration, blood utilization, and hydroxyurea (HU) therapy.

Hb S-β-thalassemia: molecular, hematological and clinical comparisons

Clinical and hematological features are presented for 261 patients with identified β-thalassemia (β-thal) mutations. Mutations causing Hb S [β6(A3)Glu→Val]-β(0)-thal were IVS-II-849 (A>G) in 44%, frameshift codon (FSC) 6 (-A) in 14%, Hb Monroe [β30(B12)Arg→Thr] in 14%, and IVS-II-1 (G>A) in 10%. Mutations causing Hb S-β(+)-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-β(+)-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-β(0)-thal mutations, but among the three mutations causing Hb S-β(+)-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-β(0)-thal and Hb S-β(+)-thal type I were generally severe, and Hb S-β(+)-thal type III disease with the -88 mutation was milder than that caused by the polyA mutation.

Phenotype/genotype relationships in sickle cell disease: a pilot twin study

The roles of genetic and non-genetic factors in the haematology, growth and clinical features of sickle cell disease have been studied in nine identical twin pairs (six homozygous sickle cell disease, three sickle cell-haemoglobin C disease). A comparison group of 350 age-gender matched sibling pairs, selected to have an age difference of <5 years, was used for assessing the concordance of numerical data. Attained height, weight at attained height, fetal haemoglobin, total haemoglobin, mean cell volume, mean cell haemoglobin and total bilirubin levels showed significantly greater correlation in identical twins than in siblings. Twins showed similarities in the prevalence and degree of splenomegaly, susceptibility to priapism, and in onset of menarche, but other clinical complications were discordant in prevalence and severity. These findings suggest that physical growth and many haematological characteristics are subject to genetic influences, but that non-genetic factors contribute to the variance in disease manifestations.

Subclassification of HbS syndrome: is it necessary?

Sickle beta-thalassaemia (S beta-thalassaemia) is a condition, which results from coinheritance of a sickle cell gene and a beta-thalassaemia gene. The clinical phenotype depends on the type of beta-thalassaemia gene (beta+ or beta(o)). There are several similarities in clinical and haematological features, which sometimes pose a difficulty in correct diagnosis. A definitive diagnosis is required in order to initiate early supportive treatment in patients with homozygous sickle cell disease (SS disease) and to define the later clinical course. Forty-seven cases of haemoglobin sickle syndrome (HbS syndrome) were studied. The clinico-haematological features and high-performance liquid chromatography (HPLC) results from 17 patients with S beta-thalassaemia were compared with those of SS disease (10 patients). Splenomegaly was more commonly found in patients with S beta-thalassaemia. Among the haematological features, red blood cell counts and HbA2 levels were significantly higher in patients with S beta-thalassaemia, while red cell indices, such as MCV, MCH were significantly lower than those seen SS disease. MCHC, PCV total haemoglobin (Hb), HbS, A and HbF were similar in the two groups.

Heterocellular hereditary persistence of fetal haemoglobin affects the haematological parameters of beta-thalassaemia trait

To assess and define the effects of heterocellular hereditary persistence of fetal haemoglobin (HPFH) on the haematological phenotype of heterozygous beta-thalassaemia, we have studied a large kindred that included a total of 204 subjects with 60 beta-thalassaemia carriers, of whom 35 were also heterozygous, and five homozygous, for heterocellular HPFH. The study was possible because of the homogeneity of the beta-thalassaemia mutation and the ability to genotype the heterocellular HPFH allele. Heterocellular HPFH had a significant effect on the mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV) and haemoglobin (Hb) A2 values in the beta-thalassaemia carriers and accounted for 29%, 30% and 24% of their respective variances. beta-thalassaemia subjects with heterocellular HPFH had higher MCV and MCH values, concomitant with lower levels of Hb A2, and a reduced ineffective erythropoiesis. We conclude that co-inheritance of heterocellular HPFH leads to a primary increase in gamma-chain synthesis in beta-thalassaemia trait and can be another confounding factor in the use of red cell indices and Hb A2 levels in population screening for beta-thalassaemia.

Jamaican Sbeta+-thalassaemia: mutations and haematology

The sickling disorders are a common cause of morbidity and mortality in Jamaica. Sickle cell beta+-thalassaemia is the fourth commonest form, occurring in one in every 3000 births. This is a heterogeneous condition, producing HbS, HbF and HbA2 with variable amounts of HbA, depending on the mutation and, within a defined population, only a few beta-thalassaemia mutations occur at high frequency. This study establishes the frequency of beta-thalassaemia mutations in Sbeta+-thalassaemia patients in Jamaica. In addition, comparison of the haematological phenotypes is possible by looking at the 'average steady-state haematology' of the different mutational groups. Blood samples from 132 unrelated Sbeta+-thalassaemia patients attending the MRC Sickle Cell Unit at the University of the West Indies were analysed by amplification refractory mutation system (ARMS) polymerase chain reaction (PCR) or sequencing to determine the nature and frequencies of the underlying beta-thalassaemia mutations. Ten mutations were identified, four of which accounted for 93% of patients studied. These were -29(A --> G) in 71 (54%), -88(C --> T) in 27 (20%), polyA(T --> C) in 17 (13%) and IVS1-5(G --> C) in nine (7%). The six remaining mutations found at low frequency were C24(T --> A) in two patients and one each of IVS2-848(C --> A), -90(C --> T), IVS1-5(G --> T), IVS1-5(G --> A) and IVS1-6 (T --> C). In one individual, no mutation was found. The three commonest mutations were all associated with haemoglobin levels of greater than 10 g/dl, whereas IVS1-5 (G --> C) had a more severe haematological phenotype. The predominance of -29(A --> G) and -88(C --> T) is in keeping with other studies on populations of African origin. IVS1-5(G --> C) is found chiefly in Indian populations, and all affected families acknowledged Indian ancestry, reflecting the prominent Indian community in Jamaica.

Benign clinical course in homozygous sickle cell disease: a search for predictors

AIMS

(1) To estimate the proportion of subjects with homozygous sickle cell disease who have a benign clinical course, and (2) to assess factors that may be predictive of benign disease.

MATERIAL

Subjects (n = 280) were participants in a longitudinal cohort study of sickle cell disease. They were classified as benign or control based on clinical history from birth to age 13 years old. Associations with growth, hematology, and an index of social status were investigated.

RESULTS

Benign disease occurred in 43 (15%) patients. Neither growth nor social status were related to benign disease. There were only two statistically independent associations: alpha thalassemia status and average steady state fetal hemoglobin (HbF). Patients with a normal complement of alpha globin genes were 2.2 (1.0, 4.9) times more likely to have benign disease than those with gene deletion, and were less likely to have frequent painful crises, dactylitis, and bone necrosis. The odds of having benign disease were 1.09 (1.02, 1.17) times higher for each unit increase in HbF, and 44% of subjects with HbF in the top decile (HbF > 13.8%) of the distribution had benign disease. There was no evidence for a threshold effect of high HbF on benign disease.

CONCLUSION

A benign clinical course of sickle cell disease may occur in Jamaica and is associated with a normal alpha globin gene complement, and high levels of HhF. Ability to predict benign disease at birth is limited.

Avascular necrosis of the femoral head in Saudi Arabians with homozygous sickle cell disease - risk factors

Avascular necrosis of the femoral head (ANFH) in Saudi patients with homozygous sickle cell (SS) disease attending King Faisal Specialist Hospital and Research Centre (KFSH&RC) occurred in 29/118 (24.6%) patients or 32% of patients aged 10 years and above. This high prevalence was heavily influenced by symptomatic selection. Contrary to observations in patients of African origin, ANFH in Saudi subjects was not associated with high hemoglobin, low fetal hemoglobin levels or with alpha thalassemia. Bone densitometry failed to detect differences in bone mineral density or content between patients with and without ANFH. Levels of 25-OH vitamin D did not differ between patients with and without ANFH. Several patients showed very rapid and complete destruction of the femoral head suggestive of osteomyelitis of the femoral head or a pyogenic arthritis. ANFH appears common in Saudi patients with SS disease although an accurate prevalence is unknown. The lack of relationship with risk factors for ANFH identified in African SS disease highlights the need for further study in the Saudi SS population.

Thalassemia: genotypes and phenotypes

The large degree of phenotypic heterogeneity of thalassemia can now be related to the underlying genomic defects. This information has accumulated rapidly over the last years through the recent advances in molecular technology. The list of main types of thalassemia (alpha or beta) that can be differentiated includes several gene deletions (complete or partial) and point mutations (or very short deletions). These occur within the genes or across the flanking DNA sequences and apparently interfere with the expression of these genes. From a quantitative point of view, the severity of the condition is directly related to the amount of functional globin chain mRNA which is made available to the ribosomes; this may vary from zero (gene deletions, frameshift, non-sense mutations or mutations at the splice-junction nucleotides) to very little (mostly hnRNA processing mutants) or to slightly subnormal (transcriptional mutants, mutations resulting in cryptic site activation or in defective cleavage of the poly-A tail). A few hyper-unstable globin chains also produce a thalassemic phenotype. This pattern is straightforward in the alpha-thalassemias. In the beta-thalassemias, the decreased beta-chain synthesis reflects the available mRNA, but the phenotypic expression depends also on the ability of the patient to reactivate gamma-chain synthesis and complement the red cell content with hemoglobin F.

The haematology of homozygous sickle cell disease after the age of 40 years

Haematological indices have been studied in 181 patients with homozygous sickle cell (SS) disease aged 40-73 years. Cross-sectional analyses in 5-year age bands indicated age-related decreases in HbF (males only), total haemoglobin and platelet counts. Longitudinal studies within individuals confirmed the downward age-related trend in haemoglobin and platelets and also revealed a falling reticulocyte count, most significant when expressed as absolute values. Total nucleated cells also fell although the decline was significant only in females. These observations are consistent with a progressive bone marrow failure which is not explained by the commonly occurring renal impairment in older SS patients since the changes persisted in analyses confined to patients with normal creatinine levels. The mechanism of this bone marrow failure is currently unknown.

Sickle cell-beta+ thalassaemia in Orissa State, India

The clinical, haematological, and some molecular genetic features of 17 Orissan Indian patients with sickle cell-beta+ thalassaemia (S beta+ thal) are described and compared with those in 131 Indian patients with homozygous sickle cell (SS) disease. Patients with S beta+ thal had higher Hb A2 levels, and lower mean cell volume (MCV) and mean cell haemoglobin (MCH) compared to SS disease but no other haematological difference of statistical significance. High levels of Hb F occurred in both genotypes and the alpha+ thalassaemia gene frequency reached 0.47 in S beta+ thal and 0.32 in SS disease. Clinically there were no significant differences between the genotypes indicating that the low levels of HbA (3-5%) in this condition were insufficient to modify the clinical features. The thalassaemic beta globin gene is inactivated by a G----C mutation at position 5 of the first intron of the beta globin gene (IVS1-5 G----C) in all cases. This finding should facilitate the introduction of a prenatal diagnosis programme aimed at the prevention of beta thalassaemia or S beta+ thalassaemia in that population.

Comparison of homozygous sickle cell disease in northern Greece and Jamaica

The clinical and haematological features of homozygous sickle cell (SS) disease were compared in 30 Greek and 310 Jamacian patients. Deletional alpha-thalassaemia, which modifies SS disease, is rare among Greek patients, so only Jamacian patients with four alpha-globin genes were included in the control group. Greek patients had higher total haemoglobin concentration and red cell counts, and lower mean cell haemoglobin concentration (MCHC) and reticulocyte counts. They also had a more normal body build and more adults had persistent splenomegaly. Fewer had a history of leg ulceration or priapism but more reported acute chest syndrome. The comparatively mild disease in Greek patients is consistent with less haemolysis and sickling and therefore less bone marrow expansion. In the absence of amelioriating factors such as high HbF concentration or alpha-thalassaemia, these findings may be explained by the low MCHC.

The interaction of alpha thalassaemia and sickle cell-beta zero thalassaemia

The effects of alpha thalassaemia on sickle cell-beta zero thalassaemia have been studied by comparing haematological and clinical features in four subjects homozygous for alpha thalassaemia 2 (2-gene group), 27 heterozygotes (3-gene group), and 55 with a normal alpha globin gene complement (4-gene group). Alpha thalassaemia was associated with significantly higher haemoglobin levels and lower reticulocyte counts independent of the presence of splenomegaly. Contrary to expectation, alpha thalassaemia was associated with small but significant increases in mean cell volume and mean corpuscular haemoglobin concentration. Splenomegaly at age 5 years and episodes of acute splenic sequestration were significantly more frequent in the 4-gene group. There were no significant differences in painful crises, acute chest syndrome, or other clinical features.

Sickle cell-hereditary persistence of fetal haemoglobin and its differentiation from other sickle cell syndromes

Some haematological indices were compared in 13 subjects with sickle cell-hereditary persistence of fetal haemoglobin (S-HPFH) and in 10 patients with homozygous sickle cell (SS) disease and four patients with sickle cell-beta zero thalassaemia, all with fetal haemoglobin (HbF) levels of 20% or above. Sickle cell-beta zero thalassaemia could be differentiated by a high HbA2 level. S-HPFH could be distinguished from SS disease with a high HbF level by red cell count, HbF level, reticulocyte count, total haemoglobin and total bilirubin level in decreasing power of discrimination.

Sickle cell disease in Orissa State, India

A study of 131 patients with homozygous sickle cell (SS) disease in Orissa State, India, indicated that, compared with Jamaican patients, Indian patients have higher frequencies of alpha thalassaemia, higher fetal haemoglobin, total haemoglobin, and red cell counts, and lower mean cell volume, mean cell haemoglobin concentration, and reticulocyte counts. Indian patients have a greater frequency and later peak incidence of splenomegaly, and hypersplenism is common. Painful crises and dactylitis are not uncommon in Indian patients but chronic leg ulceration is rare. Homozygous sickle cell disease in Orissa is similar to that in the Eastern Province of Saudi Arabia and is very different from that in populations of West African origin.

The haematology of steady state homozygous sickle cell disease: frequency distributions, variation with age and sex, longitudinal observations

The steady state haematological characteristics observed in 1071 patients with homozygous sickle cell (SS) disease aged 5-66 years are presented. Cross sectional studies indicated that HbA2 levels were consistently higher in males but no age related change was apparent. Fetal haemoglobin levels were consistently higher in females and fell significantly in males between the 5-9 and 10-14 year age groups. Total haemoglobin was significantly higher in females before age 15 and higher in males after 20 years, a dramatic age related rise occurring in males between the 10-14 and 25-29 year age groups, and a fall in patients aged 40 years and over. The mean cell volume was consistently greater in females after 15 years and a marked age related rise occurred in both sexes between the 5-9 and 25-29 year age groups. Counts of irreversibly sickled cells were consistently higher in males. Reticulocytes fell significantly with age, while platelets and total bilirubin fell significantly after the age of 15 years. Longitudinal studies confirmed the increase in total haemoglobin levels in males over the ages 10-14 years, and a significant fall in males after the age of 30 years. Such studies also confirmed the fall in HbF in males aged 5-14 years, the increase in MCV in both sexes aged 5-29 years, and the fall in platelet counts in both sexes over the age of 20 years. These observations provide 'normal' values for patients seen elsewhere and also contribute to an understanding of factors determining the haemoglobin indices in SS disease.

Medroxyprogesterone acetate and homozygous sickle-cell disease

The haematological and clinical effects of medroxyprogesterone acetate in homozygous sickle-cell (SS) disease were assessed in a 2-year controlled crossover trial completed by 23 patients. Haematological indices remained steady during the placebo phase, but during the medroxyprogesterone-acetate phase fetal haemoglobin, total haemoglobin, red-cell mass, and red-cell survival rose significantly, and reticulocytes, irreversibly-sickled-cell counts, and total bilirubin fell significantly. Painful crises were significantly less frequent during the medroxyprogesterone-acetate than the placebo phase. These results are compatible with an inhibition of in-vivo sickling in patients with SS disease during medroxyprogesterone-acetate treatment. The mechanisms of such an effect require further study.

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.

Haematological factors associated with avascular necrosis of the femoral head in homozygous sickle cell disease

The haematological indices in 50 patients with homozygous sickle cell (SS) disease and avascular necrosis of the femoral head and in 180 patients with SS disease without this complication have been compared. Avascular necrosis of the femoral head was significantly associated with high total haemoglobin levels and with low fetal haemoglobin levels. Low fetal haemoglobin levels are associated with increased intravascular sickling. These results suggest that both intravascular sickling and the increased viscosity associated with high haemoglobin levels are related to the development of avascular necrosis of the femoral head in SS disease.

The laboratory evaluation of microcytic red blood cells

Microcytic red blood cell states are common clinical problems in both adult and pediatric age groups. The recent widespread availability of electronic blood cell counters for performing routine blood counts has increased the detection of microcytic red blood cells. Physicians must workup both symptomatic and asymptomatic patients with microcytic red blood cells before they can initiate proper therapy and/or counseling. The purpose of this review is threefold: (1) to discuss the causes of microcytic red blood cells in terms of disorders of decreased heme production vs. disorders of decreased globin production, (2) to review the clinical laboratory tests useful in differentiating microcytic red blood cell states, and (3) to present a practical approach for the laboratory workup of microcytic red blood cells.

Red cell size and the clinical and haematological features of homozygous sickle cell disease

The contribution of red cell size (mean cell volume) to the clinical and haematological manifestations of homozygous sickle cell (SS) disease has been investigated by comparing the features of two groups of patients with low (less than or equal to 80 fl) and high (greater than 95 fl) MCV values after matching for age, sex and fetal haemoglobin level. The microcytic group manifested significantly higher Hb, PCV, RBC and HbA2 levels and significantly lower reticulocyte and irreversibly sickled-cell counts. Clinical features were not less severe in the microcytic group, splenomegaly persisting for longer and painful crises were more common although the latter difference did not reach significance. The milder haematological picture associated with decreased intravascular sickling was not reflected in a more mild clinical course. It is postulated that the higher viscosity accompanying the higher haemoglobin levels in microcytic patients may offset the rheological advantages of decreased intravascular sickling.

The genetics and molecular basis of alpha thalassaemia in association with Hb S in Jamaican Negroes

We have studied seven Jamaican Negro families in whom the genes for alpha thalassaemia and the sickle cell mutation (betas) were independently segregated. Using a combination of techniques we identified two alpha thalassaemia phenotypes which resemble the severe (alpha thalassaemia 1) and mild (alpha thalassaemia 2) determinants previously described in Orientals. This study has enabled us to clearly correlate the phenotype of alpha thalassaemia with the genotype in this population. Furthermore, since in each family alpha thalassaemia was present in association with the gene for the sickle cell mutation we have determined the proportion of Hb S in the peripheral blood of individuals with the alpha alpha/alpha alpha, -alpha/alpha alpha and -alpha/-alpha genotype who are also heterozygous for the betas mutation. Genetic analysis in these families shows that in each case subjects with the alpha thalassaemia 1 phenotype are homozygous for the alpha thalassaemia 2 defect (-alpha/-alpha). We have found no instances of the genotype --/alpha alpha in this population which may explain the rarity of the severe alpha thalassaemia syndromes in Jamaica. Restriction mapping data in the alpha thalassaemia 2 homozygotes from this population shows that the (-alpha/) haplotype results from a deletion of one of the linked pair of alpha globin genes and that this has probably arisen by an unequal crossover between non-homologous alpha genes.

Haematological characteristics of the beta 0 thalassaemia trait in Sardinian children

We report red cell indices and haemoglobin (Hb)A2 levels in Sardinian children with heterozygous beta 0-thalassaemia and in normal controls aged 6 months to 12 years. Iron-deficient children and those with haematological findings indicative of alpha-thalassaemia were excluded. As in adult carriers, these subjects have significantly increased mean red cell counts and significantly reduced mean Hb levels, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), haematocrit, and mean corpuscular haemoglobin concentration. From 66 to 76% of the heterozygous beta 0 thalassaemia children examined were anaemic. MCH and MCV were within the normal range in 2.8% of these children. Serum ferritin levels showed no difference from those of normal controls.

Hb F synthesis in sickle cell anaemia: a comparison of Saudi Arab cases with those of African origin

Fetal haemoglobin (Hb F) synthesis has been studied in 22 cases of sickle cell anemia (SS) from Saudi Arabia and compared with an equal number of cases of African origin. Among the Saudi Arabs gamma chain synthesis ranged from 4.0% to 19.9% of the total non-alpha chain synthesis (mean 8.1%) while the corresponding range for the Negro cases was < 0.3% to 4.6% (mean 1.7%). In both groups the peripheral blood Hb F level was on average 3--4 times higher than the proportion synthesized, indicating that the selective survival of Hb F containing cells (F cells) was an important factor in determining the final Hb F levels. Among the Saudi Arab cases there was a significant negative correlation between the degree of F cell enrichment and either the Hb F level of the percentage gamma chain synthesis. No such correlation was observed among the Negro cases. A high proportion of the cases in both groups were carriers of alpha thalassaemia in addition to SS, but no effect of alpha thalassaemia on Hb F production was observed.

Comparison of sickle cell-beta0 thalassaemia with homozygous sickle cell disease

Clinical and haematological features in 41 patients with sickle cell-beta0 thalassaemia (Sbeta0 thalassemia) and in 123 age--sex matched controls with homozygous sickle cell (SS) disease were compared. Persistence of splenomegaly was more common and fetal loss less common in Sbeta0 thalassemia but other clinical features were similar in the two genotypes. Total haemoglobin, Hb A2, PCV, CCV, and red cell count were significantly higher and MCV, MCH, MCHC, and ISC counts significantly lower in Sbeta0 thalassaemia. Proportional reticulocyte counts were significantly lower in Sbeta0 thalassaemia but there was no difference in absolute reticulocyte counts. Persistence of splenomegaly and low ISC counts are compatible with decreased intravascular sickling which may result from the lower mean cell haemoglobin S concentration in Sbeta0 thalassaemia. If beneficial effects of a low MCHC can be confirmed then a carefully monitored trial of iron deficiency in SS disease may be a logical experimental procedure.

Beta 0 thalassemia trait in Sardinia

The red cell indices and results of globin chain synthesis in peripheral blood of obligate beta 0 thalassemia (beta 0 thal) carriers (parents of homozygous beta 0 thal children) and beta thalassemia (beta thal) carriers identified during mass screening are reported. Red cell indices were similar in obligate beta 0 carriers and in carriers diagnosed during mass screening. However there was a higher incidence of anemia in female obligate beta 0 thal carriers. In Sardinia the beta 0 thal carrier showed the usual hematological characteristics of the high Hb A2 beta thal carrier with microcytosis, hypochromia, reduced osmotic fragility; Hb F greater than 1% was found in 30% of the carriers. With MCV, MCH, osmotic fragility test (OFT) and Shine and Lal discriminant function we found 3.5%, 1.5%, 3.5% and 4.0% respectively false negatives in carrier identification. A part from one subject, all obligate carriers had elevated Hb A2 levels. The alpha/beta ratio in obligate carriers (mean +/- SD) was 1.83 +/- 0.26 (N = 30).

The determinants of irreversibly sickled cells in homozygous sickle cell disease

The relationship between the irreversibly sickled cell (ISC) count and other haematological parameters has been investigated. Positive correlations occurred with the MCH, MCHC, and with two expressions of intracellular Hb S content. Since the ISC has a high MCHC, the positive correlations with MCHC and with factors derived from the MCHC may be difficult to evaluate. Negative correlations occurred with total haemoglobin and Hb F. The MCHC was found to affect the relationship between HbF and ISC count, a low MCHC being associated with, and probably determining, lower ISC counts at any level of Hb F. It is proposed that a low MCHC may inhibit ISC formation and the practical implications of this are discussed.

The development of haemoglobin A2 in normal negro infants and in sickle cell disease

The development of haemoglobin A2 levels from birth to 3 years has been compared in normal, beta-thalassaemia trait, sickle cell (SS) disease, and S-beta-thalassaemia genotypes. Hb A2 levels were almost identical in normals and in children with SS disease at 1, 2 and 3 years. The most rapid increases in Hb A2 levels occurred before 6 months but levels were still rising at the end of the third year. Sickle cell-beta+ thalassaemia could be differentiated from SS disease by the higher Hb A2 levels between 6 months and 1 year. Insufficient data were available on S-beta o thalassaemia but since Hb A2 levels in this condition are generally higher than those in S-beta+ thalassaemia, differentiation from SS disease may may also be possible from the age of 6 months.