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HEMOGLOBIN
Vol. 28, No. 2, pp. 151–156, 2004
SHORT COMMUNICATION
Thalassemia Intermedia Due to Co-inheritance ofbb0/bb+-Thalassemia and (– –SEA) aaaaaa-Thalassemia/Hb
Westmead [aaaaa122(H5)His > Gln (aaaaa2)] in a Chinese Family
Wai-Shan Wong,1 Amy Y-Y. Chan,1 Sze-Fai Yip,2
and Edmond Shiu-Kwan Ma1,*
1Division of Hematology, Department of Pathology, The University of
Hong Kong, Queen Mary Hospital, Hong Kong,
P.R. China2Department of Medicine, Tuen Mun Hospital, Hong Kong,
P.R. China
ABSTRACT
Two brothers from a Chinese family with b-thalassemia intermedia who harbor both
a- and b-globin gene defects are described. They are both compound heterozygous for
codons 41/42 (-CTTT) b0-thalassemia and nt - 28 (A > G) b+-thalassemia mutations
together with concurrent (– – SEA) a-thalassemia (SEA) deletion. One sibling also
harbors Hb Westmead, giving an unusual genotype of b0/b+-thalassemia and (– – SEA)
a-thalassemia/Hb Westmead. With respect to the age at presentation and transfusion
requirement, this subject shows a milder clinical phenotype than his brother, most
probably explainable by the presence of Hb Westmead in addition to the SEA
deletion, which causes a further amelioration of the a-chain excess and hence a less
severe disease. For areas with high prevalence of both a- and b-thalassemia mutations,
their interactions should always be considered in genotype phenotype correlation.
Moreover, routine laboratory diagnostic strategy for non-deletional a-globin gene
*Correspondence: Dr. Edmond Shiu-Kwan Ma, Division of Hematology, Department of
Pathology, The University of Hong Kong, Queen Mary Hospital, 102 Pokfulam Road, Hong
Kong, P.R. China; Fax: +852-2817-7565; E-mail: eskma@hkucc.hku.hk.
151
DOI: 10.1081/HEM-120035917 0363-0269 (Print); 1532-432X (Online)
Copyright D 2004 by Marcel Dekker, Inc. www.dekker.com
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mutations in the Chinese may need to include Hb Westmead, as it is a common a-globin
gene mutation in our population apart from Hb Constant Spring and Hb Quong Sze.
Key Words: Thalassemia intermedia; a- and b-thalassemia interaction; Hb
Westmead; Genotype phenotype correlation.
Thalassemia is a family of genetic disorders characterized by reduced synthesis of
one or more of the globin chain subunits of the hemoglobin (Hb) molecule. Imbalance
of globin chain production that results in ineffective erythropoiesis and chronic anemia
is the major factor in the pathophysiology of the thalassemic disorders. For
geographical areas where both a- and b-thalassemia (thal) mutations are prevalent,
such as South East Asia and Southern China including Hong Kong (1), a spectrum of
clinical manifestations may result from the interaction of mutations affecting the a- and
b-globin gene loci. We describe two siblings from a Chinese family with an unusual
combination of a- and b-globin gene defects in the form of co-inheritance of b0/b+-thal
and (– –SEA) a-thal/Hb Westmead [a122(H5)His > Gln (a2)] (Table 1). The phenotypic
modification of b-thal by a concurrent a-globin chain mutation is discussed.
The proband was a 39-year-old man who presented first at the age of 8 for anemic
symptoms and recurrent chest infection. His Hb level at diagnosis was as low as 4.0 g/
dL. Physical examination showed pallor, jaundice and hepatosplenomegaly. Peripheral
blood film examination showed markedly hypochromic microcytic red cells, with many
circulating nucleated red cells. High performance liquid chromatography (HPLC)
showed the presence of Hb A, high Hb A2 (8.8%) and increased Hb F (66.0%),
consistent with b-thal intermedia. The percentages of different Hb components might
be slightly affected by blood transfusions. Cellulose and citrate gel electrophoresis
showed the presence of Hb A and increased Hb F without additional abnormal bands.
Table 1. Hematological and genotypic findings for the two siblings in this report.
Parameters Proband Brother
Sex-age M-39 M-32
Age at onset (years) 8 10
Hb (g/dL) level at diagnosis 4.0 8.0
Steady state Hb (g/dL) 7.0–7.5 7.8–8.7
MCV (fL) 63.8 58.5
MCH (pg) 19.4 18.4
Hb A2 (%) 8.8 8.0
Hb F (%) 66.0 70.2
Hb H bodies Negative Negative
a Genotype – – SEA/aa – – SEA/aWestmeadab Genotype b41/42/b– 28 b41/42/b�28
Transfusion history Every 3 months None since age 15
Ferritin (pmol/L) 1492.0 2061.0
Normal ranges for males: Hb 13.0–18.0 g/dL; MCV 80.0–96.0 fL; MCH 27.0–32.0 pg; Hb
F < 0.9%; Hb A2 2.3–3.0%, ferritin 115.0–884.0 pmol/L.
152 Wong et al.
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Hb H inclusion bodies were not detected. Genotypic studies revealed that he was a
compound heterozygote for the �28 (A > G) (b+) and codons 41/42 (-CTTT) (b0)
mutations with a co-inherited a-thal deletion (– –SEA). He required regular monthly
blood transfusions to maintain his pre-transfusion Hb level at around 8.0 g/dL. At the
age of 11, splenectomy was performed. Since then, the frequency of blood transfusions
was reduced to once every 3 months. As he became a teenager, he developed
complications related to iron overload which resulted in growth retardation,
hypogonadotrophic hypogonadism, asymptomatic cardiac dysfunction and deranged
liver function. He was put on iron chelation therapy, and the latest ferritin level at last
follow-up was 2073 pmol/L.
His younger brother, who is now 32 years of age, presented as the age of 10 with
symptomatic anemia and was diagnosed as b-thal intermedia. He required regular blood
transfusions (2 to 4 times per year), which was less frequently than his brother. His
steady state Hb level was maintained at 8.0–9.0 g/dL. Subsequently, he was lost to
follow-up from the age of 15 as he became asymptomatic. He was admitted to hospital
with a chest infection a few years ago; on physical examination he was noted to have
mild Cooley’s facies, pallor, jaundice and hepatosplenmegaly. Hematological inves-
tigations showed: Hb 8.9 g/dL, MCV 54.6 fL, and MCH 17.6 pg. Results of Hb pattern
analysis were similar to his brother, showing the presence of Hb A, high Hb A2 (8.0%)
and markedly increased Hb F (70.2%). Hemoglobin electrophoresis did not reveal any
abnormal variants or bands that corresponded to Hb H/Hb Bart’s. Again, no Hb H
inclusion bodies were detected. Genotyping studies showed identical b-thal mutations
as his brother, with concurrent compound heterozygosity for the SEA deletion and Hb
Westmead [codon 122 (CAC > CAG) (a2) mutation], i.e., – –SEA/aWestmeada configu-
ration. He achieved normal growth and sexual function. Fasting sugar and testosterone
levels were normal. An echocardiogram showed mitral regurgitation and tricuspid
regurgitation, while the left ventricular ejection fraction was normal. This notwith-
standing, his ferritin level was elevated at 3774 pmol/L, and iron chelation therapy
commenced at age 30.
It has been shown that co-inheritance of a-thal may ameliorate the clinical
phenotype of severe b-thal (2). As the pathogenesis of b-thal involves excessive
intracellular precipitation of a chains causing damage to the erythroid precursors and
intramedullary cell death, co-inheritance of a-thal reduces globin chain imbalance by
decreasing a-globin chain synthesis, and therefore, leads to a milder disease. The
proband’s younger brother also carries an additional a-globin gene mutation, Hb
Westmead. Clinically, he presented later in life and had a higher Hb level at
presentation. He also required less frequent transfusions with a transfusion-free period
of 10 years. He has not yet developed complications of iron overload despite an
elevated ferritin level. However, complications of iron overload will inevitably occur
later in life, even without transfusions, as a result of increased iron absorption due to
chronic anemia. Therefore, regular follow-up and monitoring of his Hb level together
with ferritin level and iron saturation, is still mandatory in such cases. Iron chelation
should be started promptly before complications of iron overload arise. The presence of
the XmnI Gg polymorphism and globin chain synthesis ratio, however, were not
determined in these two cases.
Diagnosis of concurrent a- and b-thal cannot rely on Hb pattern study alone, as
illustrated by the above two cases. We have also previously shown that Hb H inclusion
Thalassemia Intermedia in Chinese Family 153
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bodies are only occasionally present, or are not detectable at all in the setting of an Hb
H genotype in association with heterozygous b-thal (3). Therefore, molecular study
remains the gold standard of diagnosis of a- and b-thal interaction, which is expected
to occur in areas such as Hong Kong (1), with a high prevalence of both abnormalities.
A family study is also useful in these cases, both for phenotypic diagnosis and proper
genetic counseling.
Hb Westmead, first described by Fleming et al. (4) in 1980 in a family who
emigrated from Guangdong in Southern China to Australia, is one of the most common
Hb variants in Guangxi Province (5,6). Seven out of 738 patients attending an
Outpatient Clinic in a Center located in Guangxi, were found (by molecular analyses)
to carry the Hb Westmead variant (5). The prevalence of this variant in Hong Kong is
not known. It results from a mutation in codon 122 (CAC > CAG) of the a2-globin
gene leading to a His > Gln replacement. Hb Westmead is a slightly unstable variant,
and does not separate from Hb A by electrophoresis or isoelectric focusing (IEF) (5,7).
Diagnosis is dependent on identification of the aWestmead mutation by dot-blot hybrid-
ization using 32P-labeled synthetic oligonucleotide probes (7). The mutation creates an
StuI restriction cleavage site, and is also amenable to detection by polymerase chain
reaction (PCR) using the restriction enzyme StuI (5). We happened to identify Hb
Westmead in these two siblings and a previously reported family (8), based on nega-
tive hybridization of normal and mutant probes on dot-blot analysis for Hb Quong
Sze [a125((H8)Leu > Pro (a2); codon 125 (CTG > CCG)], which lies in close proximity
to codon 122. The presence of Hb Westmead was subsequently confirmed by direct
nucleotide sequencing of the a2-globin gene (Fig. 1). It follows, therefore, that
Hb Westmead should be considered in face of anomalous dot-blot hybridization
signal for the detection of Hb Quong Sze. More importantly, as Hb Westmead is
a common a mutant in the Chinese, apart from Hb Constant Spring [a142, Term > Gln
(a2) (TAA > CAA)] and Hb Quong Sze (G.F. Lung, Nanning, Guangxi, personal
Figure 1. Direct nucleotide sequencing of the a2-globin gene, showing the CAC > CAG mutation
at codon 122, consistent with Hb Westmead. The normal allele is absent since the patient carries the
SEA deletion on the other chromosome.
154 Wong et al.
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communication), it should be screened for in routine laboratory diagnostic strategies
for a-globin gene mutations.
There are only a few reports on the co-inheritance of the Hb H genotype and
compound heterozygozity for b-thal from Greek and Sardinian families, respectively
(9–11). In the Sardinian family, the proband, who was diagnosed as homozygous for
b0-thal and a compound heterozygote for a-thal-1 and a-thal-2, based on hematological
findings, Hb pattern analysis and globin chain synthesis ratio, behaves clinically as
b-thal major (10). On the other hand, a Greek patient, who was characterized at the
molecular level, with a three a-globin gene deletion due to (– –MED/�a� 3.7) in
association with a compound heterozygous b0/b+-thal [IVS-I-6 (T > C) and IVS-I-1
(G > A)], shows a thalassemia intermedia phenotype, although the MCH value is
markedly low at 13.9 pg, signifying that the red cells are poorly hemoglobinized (11). The
interaction of various a and b genotypes is therefore complex, and depends, to a
large extent, on whether there is residual normal a- and b-globin chain synthesis, and
the degree of imbalance. Instead of having deletional a-globin gene mutations, the
brother of our proband shows compound heterozygosity for deletional and nondele-
tional a-globin gene mutations. In terms of age at presentation and transfusion
requirements, he shows a milder clinical phenotype than the proband. This is most
probably explained by the presence of Hb Westmead in addition to the SEA deletion,
which causes a further amelioration of the a chain excess, and hence, a less severe
disease. Interestingly, similar to other cases with two b-thal alleles associated with an
Hb H genotype (9–11), the two brothers in this report showed high Hb A2 levels of 8.8
and 8.0%, respectively. While the exact cause remains to be defined, it is plausible that
the high Hb A2 levels in these cases reflect the survival advantage of red cells with
enhanced d chain production, which further reduces a chain excess and improves
overall globin chain balance.
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disease and heterozygous b-thalassaemia. Haematologica 2001; 86(4):432–433.4. Fleming PS, Hughes WG, Farmile RK, Wyatt K, Coopers WN. Hemoglobin
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Received November 22, 2003Accepted December 3, 2003
156 Wong et al.
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