Page 288 - 2021_05-Haematologica-web

Case Reports
Most homozygous α0-thalassemia incidences in SEA are caused by a homozygote SEA deletion (--SEA/--SEA).4 In homozygous α0-thalassemia patients, absence of α-glo- bin results in aggregations of Hb Bart’s (γ4), which cannot release oxygen in hypoxic tissue due to its extremely high oxygen affinity. This can damage maturing erythroid pre- cursors and causes ineffective erythropoiesis.4,5 Most homozygous α0-thalassemia fetuses die in week 24 to 38 of gestation or shortly after delivery. Recently, increasing numbers of homozygous α0-thalassemia survivors have been reported worldwide.3,6 However, most underwent at least one intrauterine intervention and the mechanism of homozygous α0-thalassemia survival, without intrauterine intervention, has been little explored.
The II1 was a 2-year-old boy from Zhaoqing city, in the Guangdong Province, southern China, and was diag- nosed with homozygote of α0-thalassemia at 16 days old, but he survived naturally, until birth, without intrauterine treatment. His parents were carriers of the SEA deletion (hematological data showed in Figure 1A). The mother, who was 20 years old at conception, received routine antenatal care in a local hospital. This was her first preg- nancy and she did not receive the specific fetal DNA analysis for thalassemia as she did not know that she was a carrier at that time. The twin had a normal ultrasonic index before the gestational age (GA) of 31 weeks, com- pared with the standard population.7,8 Hydrops, placen- tomegaly and cardiomegaly were not detected (Online Supplementary Table S2; Figure 1B and C). However, the femur lenght of II2 did not increase after 31 weeks (Figure 1C). The mother had some complications, such as polyhydramnios and pre-eclampsia (Online Supplementary Table S3), but the symptoms were not serious before 31 weeks.
The twins were born by cesarean section at 34 weeks due to severe maternal pre-eclampsia and the develop- ment of symptoms of polyhydramnios and ascites in II2. After birth, II2 showed abdominal distension and tension and died quickly. The clinical features of abdominal dis- tension, hepatosplenomegaly and anasarca led to II2
Here, we report twins with homozygote α0-tha- lassemia: the elder twin (II1 in Figure 1A) survived, whilst his twin brother (II2) was a hydrops fetus who died. Further analysis found that the elder twin’s index was significantly better than that of the younger and other reported survivors with homozygous α0-thalassemia (Online Supplementary Table S1) due to a chimera with a small amount of functional α-globin. It is the first discov- ery of a homozygous α0-thalassemia survivor related to chimerism and it is also a rare report which explores the mechanism of natural survival of homozygous α0-tha- lassemia patients.
Figure 2. Chimeric ratio analysis by polymerase chain reaction of short tandem repeat loci. There are more than two short tandem repeat (STR) peaks at one STR locus in the blood, hair follicle and oral mucosa sample from II1 and all of them were inherited from his parents.
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haematologica | 2021; 106(5)