RESUMO
BACKGROUND: Hemoglobin abnormalities constitute a public health problem in many countries in the world. In Tunisia, these disorders were thought to affect only the North-western population. However, the existence of hemoglobinosis concentration in Kebily in south Tunisia has been suggested by previous work. In order to estimate their frequencies, we performed a screening of hemoglobin abnormalities in the North-Kebili region, to establish a prevention program of the homozygous forms. METHODS: This screening concerned all 1st and 2nd grade primary school pupils in North Kebily. After a questionnaire, a blood sample was drawn from every child. Hemogram, sickling test, and hemoglobin electrophoresis at alkaline pH were performed for all children. Hemoglobin electrophoresis at acid pH and a specific hemoglobin A2 titration were performed for some children. RESULTS: The study concerned 1,400 children, aged between 5 and 12 years, the mean age was 7 years and 7 months +/- 10 months. Consanguinity rate and coefficient were respectively 44% and 2249 x 10(5). Endogamy was very high. The global rate of hemoglobin abnormalities was 9.4%. Drepanocytosis with a rate of 4.9% was the most frequent, followed by beta thalassemia (3.1%) and C hemoglobinosis (1.6%). These abnormalities were unequally distributed; very frequent in some localities, they were quite absent in others. CONCLUSIONS: This study revealed a hemoglobinosis concentration in Tunisia, which can be classified second after that of Beja in North-western Tunisia. The heterogeneous distribution of the hemoglobin abnormalities in North-Kebili region and the high consanguinity and endogamy rates constitute factors that promote homozygous and double heterozygous forms to arise and justify the elaboration of a preventive strategy.
Assuntos
Hemoglobinopatias/epidemiologia , Fatores Etários , Anemia Falciforme/diagnóstico , Anemia Falciforme/epidemiologia , Anemia Falciforme/genética , Criança , Pré-Escolar , Consanguinidade , Estudos Transversais , Doença da Hemoglobina C/diagnóstico , Doença da Hemoglobina C/epidemiologia , Doença da Hemoglobina C/genética , Hemoglobinopatias/diagnóstico , Hemoglobinopatias/genética , Heterozigoto , Homozigoto , Humanos , Modelos Genéticos , Tunísia/epidemiologia , Talassemia beta/diagnóstico , Talassemia beta/epidemiologia , Talassemia beta/genéticaRESUMO
Sickle cell anemia is a monogenic hereditary disease characterized by a mutation in the beta globin gene. Five major haplotypes associated with the beta S mutation have been defined: Benin, Bantu, Senegalian, Camerounian, and Arabo-Indian. Previous studies in northern Tunisia showed that sickle cell anemia was of Benin origin in this region. Patients from the south of Tunisia, mainly from the Kebili region, were not previously concerned. In this study, we have determined the beta S haplotype and evaluated phenotypical expression of the disease in 14 patients from this latter region. The use of four restriction endonucleases having polymorphic sites in the beta globin gene showed that all patients had the Benin haplotype, confirming the Benin origin of sickle cell anemia in Tunisia. This haplotype is associated with an heterogeneous expression of fetal hemoglobin (HbF) with extremes varying from 2.4 to 16.3% and a mean expression rate of 8.16%, which is in accordance with literature data. In spite of the haplotype homogeneity in our patients, clinical heterogeneity was noted. A unique case of alpha-thalassemia could not explain this heterogeneity. In contrast, we found a certain correlation between fetal hemoglobin expression and clinical severity.
