β‑thalassemia caused by compound heterozygous mutations and cured by bone marrow transplantation: A case report

Abstract

In the present study, a rare familial case of severe thalassemia with compound spontaneous mutations is reported. A 2.5‑year‑old boy, who suffered from severe anemia with yellowish skin, enlarged liver and spleen, was provided with a blood transfusion every 20 days to maintain hemoglobin levels between 90 and 100 g/l. Sanger sequencing combined with reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and Gap‑PCR revealed that the proband was a carrier of 4 compound heterozygous mutations: Hemoglobin subunit β (HBB):IVS‑II‑654(C>T)β+; Southeast Asian‑type‑hereditary persistence of fetal hemoglobin (SEA‑HPFH); HBB:c316‑148G>T; hemoglobin subunit α2 (HBA2):c.46G>A. The father of the proband was identified as a carrier of the heterozygous SEA‑HPFH mutation, the mother was a carrier of compound heterozygous mutations of HBB:IVS‑II‑654(C>T) and HBA2:c.46G>A, and the elder sister was heterozygous for HBB:IVS‑II‑654(C>T)β+. Based on these genetic results, it was determined that the proband had both of heavy β‑thalassemia and α‑thalassemia. Upon human leukocyte antigen matching, bone marrow transplantation (BMT) was successfully performed on the proband by selecting his HLA‑compatible sister as a donor. Following treatment, the proband was revealed to only carry the IVS‑II‑654(C>T)β+ heterozygous mutation, and further regular blood transfusions have been avoided; BMT results remained normal at six months follow‑up.

Figure 1.

Identification of our mutated genes in the proband by DNA sequencing and gel electrophoresis. Sanger sequencing of the mutations: (A) HBA2:c.46G>A; (B) HBB:c.316-148G>T; and (C) HBB:IVS-II-654(C>T)β⁺. Mutated nucleotides are outlined with a magenta box. (D) Identification of the HPFH deletion by gel electrophoresis; the lower bands indicated DNA fragment deletion in the proband (lane 1) and father (lane 2), whereas the normal controls showed one regular band (lanes 3 and 4). (E) Reverse transcription-quantitative polymerase chain reaction demonstrated that lower expression of the HPFH gene in proband and father compared to the normal control. *P<0.05 vs. control. HBA2, hemoglobin subunit α2; HBB, hemoglobin subunit β; HPFH, hereditary persistence of fetal hemoglobin; Normal controls, blood DNA samples collected from disease-free volunteers.

Figure 2.

Pedigree and genetic mutations of thalassemia in the family of the proband (arrow).

Figure 3.

The CSPX/CSPY genetic testing by fluorescence in situ hybridization indicated that the donor cells accounted for 99% in the blood of the proband 30⁺ days post-bone marrow transplantation. The red signal identifies the Y chromosome and the green signal identifies the X chromosome. XY cells were from the proband, and XX cells were from the donor sister. CSPX, centromeric specific probe for the X chromosome.