Detecting rare thalassemia in children with anemia using third-generation sequencing

In China, conventional genetic testing methods can only detect common thalassemia variants. Accurate detection of rare thalassemia is crucial for clinical diagnosis, especially for children that need long-term blood transfusion. This study aims to explore the application value of third-generation sequencing (TGS) in the diagnosis of rare thalassemia in children with anemia.

We enrolled 20 children with anemia, excluding from iron deficiency anemia (IDA). TGS was employed to identify both known and novel thalassemia genotypes, while sanger sequencing was used to confirm the novel mutation detected.

Among the 20 samples, we identified 5 cases of rare thalassemia. These included β^-4.9 (hg38,Chr11:5226187-5231089) at HBB gene, α^-91(HBA2:c.*91delT), α^CD30(HBA2:c.91-93delGAG), Chinese ^Gγ⁺(^Aγδβ)⁰(NG_000007.3: g .48795-127698 del 78904) and delta ^{- 77(T > C)}(HBD:c.-127T>C). Notably, the -^SEA/α^-91α genotype associated with severe non-deletional hemoglobin H disease (HbH disease) has not been previously reported. Patients with genotypes β⁶⁵⁴/β^-4.9 and -^SEA/α^-91α necessitate long-term blood transfusions, and those with the -^SEA/α^CD30α, Chinese ^Gγ⁺(^Aγδβ)⁰ and delta thalassemia demonstrate mild anemia.

TGS demonstrates promising potential as a diagnostic tool for suspected cases of rare thalassemia in children, especially those suspected to have transfusion-dependent thalassemia (TDT).