Prenatal diagnosis of ß-thalassemia in twin pregnancies in Iran.

OBJECTIVE: Prenatal diagnosis of ß-thalassemia carrier couples has helped to prevent bearing affected children. Among 177 couples referred to our laboratory for prenatal diagnosis, 14 mothers had twin pregnancies.  METHODS: By using direct and indirect methods, we determined their mutations and linkage analysis using polymorphic markers (restriction fragment length polymorphism [RFLP]).  RESULTS:  It was shown that in five families both fetuses were heterozygote carriers. In another five families, one fetus was normal and the other one was carrier. In two families, one fetus was affected and the other one was heterozygous carrier; in one case one fetus was affected and the other one was homozygote normal. In the last family both fetuses were homozygote normal. If all fetuses were fraternal then one would expect to see seven homozygote normal and the same number affected, and 14 carriers. CONCLUSION: Our results indicated that at least in cases where both fetuses had identical genotypes, then they may be identical twins. Molecular testing indeed showed that in three cases the twins were identical. Another point is that in three cases, one of the twin fetuses was affected and the other one was either normal or heterozygote in which only the affected fetuses were aborted by the specialist.

Co-inheritance of hemoglobin D and ß-thalassemia traits in three Iranian families: clinical relevance.

Here we report the result of three cases referred to our lab that had a combination of ß-thalassemia and hemoglobin D (Hb D) traits. These individuals had no symptoms of profound anemia and hematological indices were similar to that of a ß-thalassemia heterozygote. In all three cases, the Hb D level was elevated and no HbA was detected electrophoretically. The electrophoresis pattern suggested that all cases were homozygotes for Hb D. PCR followed by digestion with EcoRI and sequencing of the ß-globin gene confirmed the presence of Cd 121 GAA>CAA in the heterozygous form with another ß-globin mutation. In all cases, the mutations in the ß-globin gene were detected by ARMS PCR technique and they were either IVSII-I or IVSI-5. Hematological studies of the family members showed that thalassemia which caused the mutations and Hb D were in the trans position.