High prevalence of hemoglobin disorders and glucose-6-phosphate dehydrogenase (G6PD) deficiency in the Republic of Guinea (West Africa).

Reliable and accurate epidemiological data is a prerequisite for a cost effective screening program for inherited disorders, which however, is lacking in a number of developing countries. Here we report the first detailed population study in the Republic of Guinea, a sub-Saharan West African country, designed to assess the frequency of glucose-6-phosphate dehydrogenase (G6PD) deficiency and hemoglobinopathies, including screening for thalassemia. Peripheral blood samples from 187 Guinean adults were screened for hemoglobin (Hb) variants by standard hematological methods. One hundred and ten samples from males were screened for G6PD deficiency by the fluorescent spot test. Molecular analysis was performed for the most common α-thalassemia (α-thal) deletions, ß-globin gene mutations, G6PD variants B (376A), A (376G), A- (376G/202A) and Betica (376G/968C), using polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP) or sequencing. Of the 187 subjects screened, 36 were heterozygous for Hb S [ß6(A3)Glu→Val, GAG>GTG] (allele frequency 9.62%). Sixty-four subjects were heterozygous and seven were homozygous for the -α(3.7) kb deletion (allele frequency 20.85%). ß-Thalassemia alleles were detected in five subjects, four with the -29 (A>G) mutation (allele frequency 1.07%) and one with codon 15 (TGG>TAG) (allele frequency 0.96%). The G6PD A- and G6PD Betica deficient variants were highly prevalent with a frequency of 5.7 and 3.3%, respectively. While we did not test for ferritin levels or α(0)-thal, four females (5.2%) had red cell indices strongly suggestive of iron deficient anemia: Hb <9.7 g/dL; MCH <19.3 pg; MCV <68.2; MCHC <31.6 g/dl; RDW >19.8%. Our results are consistent with high frequency of alleles such as Hb S, α-thal and G6PD deficient alleles associated with malaria resistance. Finding a 9.6% Hb S allele frequency supports the notion for a proficient neonatal screening to identify the sickle cell patients, who might benefit from early prophylactic treatment for infections. The incidence of significant iron deficient anemia in women is lower than expected in an under developed country.

Chloride channel 7 (CLCN7) gene mutations in intermediate autosomal recessive osteopetrosis.

Osteopetrosis is a heterogeneous group of inherited disorders that includes a malignant autosomal recessive form, an intermediate autosomal recessive form and autosomal dominant forms of the disease. Most malignant osteopetroses have been ascribed to mutations in the OC116 gene encoding the human a3 subunit of vacuolar H(+)-ATPase. Few cases of autosomal recessive malignant osteopetrosis have been ascribed to mutations in the chloride channel 7 gene (CLCN7), which accounts for all autosomal dominant type II cases reported to date. Up until now, however, nothing has been known regarding the molecular basis of the intermediate form of osteopetrosis (IARO). Our study of two Portuguese IARO families shows that homozygosity for ClCN7 mutations also accounts for this form of osteopetrosis. The two patients presented with spontaneous fractures in the first years of life and generalised increase of bone density. Direct sequencing of the ClCN7 gene in both patients revealed homozygosity for two mutations (G203D and P470Q). We conclude therefore that ClCN7 mutations not only account for some dominant and malignant forms but also for intermediate forms of osteopetrosis.