Hb SKMC and an unprecedented γδβ-thalassemia: first report from Iraq

Thalassemias are genetic disorders of globin chain synthesis. In Iraq, β-thalassemia is more prevalent than α-thalassemia. This study identifies two unpredicted globin gene mutations, a rare α-globin gene mutation (Hb SKMC) and a novel γδβ-thalassemia deletion.

Over 2 years, the Genetics unit at PAR hospital in Erbil, northern Iraq processed 137 β-thalassemia and 97 α-thalassemia genetic testing requests. Three symptomatic thalassemia cases with unreported genotypes were identified. Proband-1α and proband-2α had Hb H disease, while proband-1β had severe transfusion-dependent β-thalassemia (TDT). Molecular studies included multiplex PCR, reverse hybridization, multiplex ligation-dependent probe amplification (MLPA), and globin gene sequencing.

The α-thalassemia probands exhibited moderate microcytic hypochromic anemia with irregular transfusions and splenomegaly. Hb H disease was confirmed by positive Hb H tests and high-performance liquid chromatography (HPLC). Molecular analysis revealed heterozygous -^MED deletion in proband-1α and α2^Poly-A2 mutation in proband-2α. Sequencing identified the Hb SKMC (HBA1:c.283_300+3dup) mutation in both probands. The β-thalassemia proband showed anemia and regular transfusions. Molecular studies detected the IVS1.110 G>A mutation and a novel γδβ-thalassemia deletion in compound heterozygous form. The maternal sample showed the IVS1.110 G>A mutation, and MLPA confirmed the γδβ-thalassemia deletion in the paternal sample.

These findings highlight the genetic diversity of thalassemias in the region and emphasize the importance of advanced molecular diagnostics in detecting rare mutations.