Thalassemia in Western Australia: 11 novel deletions characterized by Multiplex Ligation-dependent Probe Amplification.

The number of immigrants in Western Australia from many different areas where hemoglobinopathies are endemic has increased dramatically since the 1970s. Therefore, many different thalassemia mutations have been introduced in the country, which add a technological diagnostic problem to the serious burden of hemoglobinopathy management and to public health care. Recently, we have developed a rapid and simple technique based on Multiplex Ligation-dependent Probe Amplification to detect deletions causing alpha-and beta-thalassemia, deltabeta-thalassemia and Hereditary Persistence of Fetal Hemoglobin. A screening for (unknown) deletions was performed in a cohort of patients of different ethnic backgrounds preselected for their thalassemia phenotype, in which common deletions and point mutations were excluded. Out of 37 cases suspected to carry a deletion, 27 were found to carry 17 different deletion types of which 6 causing alpha-thalassemia and 5 causing beta-thalassemia were novel. For 3 of the deletions, we have been able to characterize the exact breakpoint sequences by long-range PCR and direct sequencing. These results show that MLPA is a suitable technology to detect unknown and uncommon deletions. These could represent a diagnostic problem when offering prevention to couples at risk presenting with unclear phenotypes and might result in a serious fetal problem when the deletion involves embryonic genes.

Two new alpha1-globin gene point mutations: Hb Nedlands (HBA1:c.86C>T) [alpha28(B9)Ala-->Val] and Hb Queens Park (HBA1:c.98T>A) [alpha32(B13)Met-->Lys].

We report two new point mutations of the alpha1-globin gene found in a Greek and a Burmese patient, both living in Western Australia. The patients were initially selected for their microcytic hypochromic parameters as belonging to a group suspected for uncommon (deletion) defects. Gap-polymerase chain reaction (gap-PCR) and multiplex ligation-dependent probe amplification (MLPA) technologies were applied, and in those cases not showing deletions, direct sequencing was performed. We have found 1) HBA1:c.86C>T, Hb Nedlands [alpha28(B9)Ala-->Val] which, based on the red cell indices and phenotype prediction scores, is presumed to be clinically silent, and 2) HBA1:c.98T>A, Hb Queens Park [alpha32(B13)Met-->Lys] which seems to be associated with a mild alpha-thalassemia (alpha-thal) phenotype. The phenotype/genotype correlation is briefly described.

A moderately severe alpha-thalassemia condition resulting from a combination of the alpha2 polyadenylation signal (AATAAA-->AATA- -) mutation and a 3.7 Kb alpha gene deletion in an Australian family.

We have recently studied a family with a rare combination of two abnormal alpha-globin genes. The combination of a two-base (AA) deletion in the alpha2 polyadenylation signal (poly A) (AATAAA-->AATA- -) and a 3.7 kb alpha gene deletion, found in two children, resulted in a moderately severe thalassemic condition. Both parents and three siblings were tested and the hematological condition and molecular findings are presented. The father was born in India with Portuguese and British ancestry; the mother is of Dutch ancestry. All three siblings were born in Australia.

The prevalence and molecular basis of hemoglobinopathies in Cambodia.

Blood counts, hemoglobin (Hb) high performance liquid chromatography (HPLC), and DNA analyses were performed on 260 children, aged 5 months to 16 years, at Siem Reap to assess the prevalence of thalassemia and other hemoglobinopathies in regional Cambodia. Hemoglobinopathies were present in 134 children (51.5%) with 20 abnormal genotypes identified. alpha-Thalassemia (thal) (35.4%) was the most prevalent disorder and the -alpha3.7 gene deletion was the most common alpha-globin gene abnormality. The - -SEA deletion and nondeletional forms of alpha-thal, Hb Constant Spring [Hb CS, alpha142, Term-->Gln, TAA-->CAA (alpha2)], Hb Paksé [alpha142, Term-->Tyr, TAA-->TAT (alpha2)] and triplicated alpha genes, were also present but at low frequencies. Hb E [beta26(B8)Glu-->Lys, GAG-->AAG] (28.8%) was the most common beta-globin gene abnormality, whilst beta-thal was only detected in two children (0.8% of cases). Although hemoglobinopathies were common, the majority of abnormalities detected (heterozygous -alpha3.7 and Hb E) were not clinically significant. On the basis of these findings, and with the majority of abnormalities being mild, it seems improbable that thalassemia represents a major health burden in this region of Cambodia.

Hemoglobinopathies in the Christmas Island population.

Christmas Island is a remote Australian territory 2,400 km north of Perth. Health care is administered from Perth. The population is predominantly Chinese, with some Malay, Indian and European. As hemoglobinopathies are known to be common amongst these ethnic groups, a study was performed to determine their prevalence and significance in the Christmas Island population. Three-hundred and sixty-four individuals (adults and children) were tested. All subjects were assessed by full blood count, alpha-globin multiplex polymerase chain reaction (PCR) and PCR testing for Hb Constant Spring [alpha142, Term-->Gln, TAA-->CAA (alpha2)]. Microcytic patients (MCV <80 fL) were further investigated by high performance liquid chromatography (HPLC) and serum ferritin was determined. Where present, beta-thalassemia (thal) mutations were characterised by PCR. Thirty-four subjects (9.3%) were microcytic and of these five were iron deficient. The remainder were heterozygous for a hemoglobinopathy, giving a 9.1% incidence of hemoglobinopathies in Christmas Islanders. alpha-Thalassemia was identified in 23 subjects, seven of whom were heterozygous for alpha(-3.7); the remaining 16 were heterozygous for the - -SEA deletion. One case of heterozygous deltabeta-thal and one case of heterozygous Hb E [beta26(B8)Glu-->Lys] was detected. Of the eight subjects heterozygous for beta-thal, at least five mutations are represented, indicating a diverse and heterogeneous origin for this population.

Hemoglobin Titusville, a low oxygen affinity variant hemoglobin, in a family of Northern European background.

We report the second case of Hb Titusville in a family of Northern European background. This variant hemoglobin caused by an alpha-globin gene mutation has decreased oxygen affinity. Correct diagnosis is clinically important to spare affected individuals extensive investigations into other causes of low oxygen saturation in peripheral blood.