The frequency and distribution pattern of B-thalassemia mutations in Turkey

ß-thalassemia, a-thalassemia and sickle cell anemia are the three most common hemoglobinopathies in Turkey. ß-thalassemia major makes up 73%, sickle cell anemia 23% and Hb H disease 4% of total patients with hemoglobinopathy. The overall frequency of ß-thalassemia is 2%. However, the frequency shows regional variations and in some areas it is as high as 13%. Molecular studies indicated the presence of more than 35 different mutations associated with ß-thalassemia. In this study it was shown that five different mutations, namely IVSI-110 (G-A), IVSI-6 (T-C), IVSII-1 (G-A), IVSII-745 (C-G) and IVSI-1 (G-A) make up 71% of all ß-thalassemia mutations. The rate of consanguineous marriage in families with thalassemia major is %63. However, in 11% of these families, parents carry two different thalassemia mutations. The IVSI-1 (GÆA) mutation is most prevalent in the Aegean Region and it seemed that this mutation moved from this region toward Marmara, Black Sea, Middle, East and South-eastern Anatolia. The IVSII-745 (C-G) is most prevalent in the Mediterranean region and it moved toward Central Anatolia, Black Sea and South-eastern Anatolia. Contrary to these two mutations FSC8 (-AA), IVSII-1 (G-A) and -30 (T-A) mutations are most prevalent in Eastern Anatolia and they moved from this region to South-eastern Anatolia, Mediterranean Region, Central Anatolia and Aegean Region. The frequency of various mutations in Central Anatolia is very close to the mean figures given for Turkey indicating that these mutations are well mixed in this region. Sickle cell anemia and sickle cell ß-thalassemia are almost exclusively seen in eastern coast of Mediterranean Sea and in Thrace. In Turkey, ß-thalassemia mutations are very heterogeneous although frequencies of these mutations show some regional differences there is no specific that ß-thalassemia mutation or distribution pattern that would aid in the identification of any ethnic background.