Sickle cell gene in the population of Saudi Arabia

A comprehensive screening program was initiated in Saudi Arabia in 1982 to determine the frequency of the sickle cell (Hb S) gene in the different regions of Saudi Arabia. Over a period of 10 years 30,055 samples were collected from 36 areas in the five provinces of Saudi Arabia; these were screened using electrophoretic techniques in alkaline and acid pH for the presence of Hb S in heterozygous and homozygous states. The overall prevalence of Hb AS was 7.36% and Hb SS was 1.06%, giving an Hb S gene frequency of 0.047. The results from the different regions were separated and the prevalence of Hb AS and Hb SS and Hb S gene frequencies were calculated in each province and each region. The prevalence of Hb AS and Hb SS cases ranged from O to 25.88% and O to 5.27%, respectively. No case of Hb AS or Hb SS were identified in certain areas of the central province (Al-Russ, Al-Unaiza, Al-Mesnab and Bkaria) and northern province (Qurayat and Al-Jouf). In the southern province both Hb S homozygotes and heterozygotes were encountered in all regions except Farasan Island. In all other regions the Hb S gene was encountered, but at a variable frequency. Applying Hardy-Weinberg equilibrium it was observed that in the majority of the regions the observed Hb S homozygotes were significantly higher compared to the number expected (p < 0.0001). This was believed to be due to bias as the samples were collected in the hospital. The Hb S gene frequency in the different regions ranged from 0 to 0.17 when the frequency was calculated on the basis of both Hb AS and Hb. SS cases, and 0 to 0.13 if the gene frequency was calculated after eliminating the Hb SS cases. A close correlation was observed between the Hb S gene frequency and malaria endemicity. This study shows that the Hb S gene occurs frequently in several regions of Saudi Arabia and there is an urgent need to implement control and prevention programs to reduce the number of Hb S homozygous cases.

Molecular defects in beta-thalassaemias in the population of Saudi Arabia

The beta-thalassaemias are a heterogeneous group of inherited disorders caused by mutations in and around the structural gene of the beta-chain of the adult haemoglobin (HbA). Studies at the gene level have identified a large number of beta-thalassaemia gene variations in different populations. These findings have implications for the use of molecular diagnosis for genetic counselling and prenatal detection of the beta-thalassaemias. In our unit, we initiated studies to investigate the molecular defects in beta-thalassaemias in Saudi Arabia using amplification-refractory mutation systems, dot blot analysis and restriction endonuclease analysis, and identified mutations producing beta(+)- and beta zero-thalassaemias. Twenty of the mutations encountered in the Asian, Mediterranean, Chinese and other Arab populations were investigated. The most commonly encountered mutations in Saudi beta-thalassaemia patients were IVS-I-110, IVS-II-1, CD 39, IVS-I-5 and IVS-I 3' end (-25), while frameshifts at CD 8/9, Cap+1 (A-->C) and CD 6 mutations were identified at a low frequency. These mutations account for 84.94% of the total beta-thalassaemia mutations. The remaining 15% remain unknown. This is the first report on the type and nature of mutations in Saudi beta-thalassaemia patients. It presents frequencies of twenty mutations and emphasises the need for further detailed investigations to clarify the whole spectrum of beta-thalassaemia mutations in the Saudi population.

Consanguinity among the Saudi Arabian population

This study was conducted on 3212 Saudi families to investigate the prevalence of consanguineous marriages. The families were interviewed and the information on the relationship between the husband and wife was obtained. The overall rate of consanguinity shows that 57.7% of the families screened were consanguineous. The most frequent were first cousin marriages (28.4%) followed by distant relative marriages (15.2%) and second cousin marriages (14.6%). The families were grouped according to the province of their origin and the consanguinity rates were calculated accordingly. There were slight differences in the consanguinity rates in the five provinces, which ranged from 52.1% to 67.7%. In each province first cousin marriages were the most frequently encountered pattern, ranging from 17.9% to 40.9%. The inbreeding coefficient (F) was calculated for each province and ranged from 0.020 to 0.030. Within each province, there were several significant differences among the populations in the different areas. The highest rate of consanguinity was 80.6% in Samtah and the lowest rate was around 34% in Abha in the South Western province. These results place Saudi Arabia among the countries of the world with a high rate of consanguinity. The possible consequences of increased consanguinity are presented and discussed.

The frequency of 14 beta-thalassemia mutations in the Arab populations

The beta-thalassemias are a heterogeneous group with respect to molecular pathogenesis, and different populations and ethnic groups differ with respect to the predominating mutations. This variable spectrum of beta-thalassemia mutations has resulted in extensive studies in each population and ethnic group to identify the major mutations. In this study we investigated the prevalence of 14 mutations in 253 beta-thalassemia patients drawn from eight Arab countries (i.e. Jordan, Egypt, Syria, Lebanon, Yemen, and Saudi Arabia), living in Saudi Arabia and attending Ministry of Health hospitals. The mutations investigated included IVS-I-110 (G-->A), IVS-II-1 (G-->A), IVS-I-5 (G-->C), codon 39 (C-->T), IVS-I-1 (G-->A), frameshift at codons 8/9 (+G), frameshift at codons 41/42 (-TTCT), codon 15 (TGG-->TAG), IVS-I-6 (T-->C), frameshift at codon 16 (-C), IVS-II-745 (C-->G), codon 6(-A), IVS-I, 3' end (-25 bp), and Cap +1 (A-->C). The most frequently encountered mutations were IVS-I-110 and IVS-II-1 which were identified in the population of each Arab country. The IVS-I-1 and IVS-II-745 mutations were encountered in Jordanians, Egyptians, and Syrians. The IVS-I-5, codon 39, codon 6, IVS-I, 3' end (-25 bp), and Cap +1 mutations were encountered only in Saudis and not in other Arabs, except codon 39 which was present in the Syrians and Lebanese. Other mutations were generally rare and not specific to any Arab ethnic group. This paper presents preliminary data on the prevalence of 14 mutations in the Arab populations and shows wide variation in the molecular basis of beta-thalassemia in different Arab ethnic groups. Further detailed studies to identify the entire spectrum of beta-thalassemia mutations are stressed.

Genetic compounds--Hb S, thalassaemias and enzymopathies: spectrum of interactions

In areas with high occurrence of the red cell genetic abnormalities, i.e. sickle cell gene, alpha- and beta-thalassaemias, and glucose-6-phosphate dehydrogenase deficiency, various genes frequently co-exist in the same population. Co-inheritance of two or more abnormal genes in the same individual is frequently encountered, particularly in certain 'closed' tribes in Arabia in which consanguinity is the norm. Such genetic interactions modify the clinical presentations of the disease state. During our studies, we encountered a large number of individuals who were carriers of two or more abnormal genes. The most frequent genetic compounds were double heterozygous HbS-beta zero-thalassaemia and HbS-beta(+)-thalassaemia with associated alpha-thalassaemia or G-6-PD deficiency. Clinical history, and assessment, as well as blood analysis for haematological, biochemical, and molecular pathology determinants were carried out. The patients were classified into subgroups, based on the genetic findings. The clinical, haematological and biochemical data were assessed separately for each group. Sickle cell anaemia (Hb SS) cases, without any other abnormal gene, were used as a reference group. The results showed severe anaemia in patients with HbS/beta zero-thalassaemia and associated alpha-thalassaemia and/or G-6-PD deficiency. Patients with HbS/beta zero-thalassaemia exhibited features similar to that of the sickle cell anaemia. While sickle cell anaemia patients with alpha-thalassaemia and G-6-PD deficiency exhibited a milder presentation. This paper presents various forms of genetic associations, their influence on the clinical presentation and the laboratory parameter data, and discusses the implications of the findings.

Case studies on haemoglobin S heterozygotes with severe clinical manifestations

Generally, individuals who are heterozygous to haemoglobin S (Hb AS) are asymptomatic and do not present any haematological or clinical manifestations. However, other associated genetic abnormalities may influence the presentation in Hb AS cases. This study was conducted on twenty children heterozygous for HB S who presented clinical manifestations similar to those of sickle cell anaemia. All these children had anaemia associated with several red cell morphological abnormalities. The white blood cell counts were elevated in all patients and differential count studies showed a substantial increase in lymphocytes and polymorphonuclear leucocytes in the majority of the cases. Forty-five per cent of the patients had associated alpha-thalassaemia, 60 per cent had beta-thalassaemia, 30 per cent had G-6-PD deficiency and 10 per cent had partial glutathione reductase deficiency. Pyruvate kinase activity was normal in all cases. Riboflavin deficiency was encountered in 30 per cent of the patients and iron deficiency in 15 per cent of these Hb S heterozygotes. The major clinical findings were splenomegaly, hepatomegaly, and vaso-occlusive crisis. The majority of the patients had received blood transfusions. The hand and foot syndrome was identified in three (15 per cent) of the patients. The haematological and clinical findings in these twenty Hb S heterozygotes are presented in this paper and the possible causes for these abnormalities are discussed.

Effect of alpha thalassaemia, G-6-PD deficiency and Hb F on the nature of sickle cell anaemia in south-western Saudi Arabia

This study was conducted on sickle cell anaemia (SCA) patients from the south-western province (SWP) of Saudi Arabia to determine the effect of thalassaemias, glucose-6-phosphate dehydrogenase (G-6-PD) deficiency and Hb F level on the clinical presentation of sickle cell anaemia. The results showed that associated alpha-thalassaemia improved the haematological parameter values while associated G-6-PD deficiency and high Hb F level did not play a significant role in amelioration of the disease in these patients. Hb S/beta(0) -thalassaemia cases showed a severe anaemia similar to the SCA patients without alpha-thalassaemia. However, considerable improvement of the haematological parameters were found in patients with S/beta(0)-thalassaemia and associated alpha-thalassaemia. This paper reveals that alpha-thalassaemia may partially ameliorate the clinical manifestations of SCA in Saudi patients from the SWP, while high Hb F level and G-6-PD deficiency do not modify SCA to any statistically significant extent.

Functional health development model: a tool for planning

This paper describes a functional model (gross style) taking available information about the health sector e.g. indicators of health status, types of service utilization, source allocations and placing these quantities into a systematic framework as a tool for planning for health services in a developing area. The major advantages of functional models over trial-and-error for planning have been presented. The functional model described could contribute to the sorting out of desirable from less desirable policy alternatives for a specific population. The output from the model is useful for matching resources to program development, taking into consideration costs and effectiveness.