2009 Vienna - European Society of Human Genetics

Clinical genetics and Dysmorphology
result. It can be suggested that when one couple carry a severe form
of alpha-thal as cis the other partner should be checked for alpha-gene
mutation even if he is carrier of beta-thal.
P02.179
Segmental duplications involving the α-globin gene cluster as a
modulating factor in β-thalassemia intermedia.
C. L. Harteveld 1 , M. Phylipsen 1 , M. Tischkowitz 2 , A. Will 3 , B. Clark 4 , S. Thein 5,6 ,
P. Giordano 1 ;
1 Laboratory for Diagnostic Genome Analysis, Leiden, The Netherlands, 2 Departments
of Human Genetics, Oncology and Medicine, Jewish General Hospital,
McGill University, Montreal, QC, Canada, 3 Royal Manchester Children’s
Hospital, Hospital Road, Pendlebury, Manchester, United Kingdom, 4 Department
of Haematological Medicine, Kings College Hospital, Bessemer Road,
London, United Kingdom, 5 of Haematological Medicine, Kings College Hospital,
Bessemer Road, London, United Kingdom, 6 King’s College London School of
Medicine, Molecular Haematology, James Black Centre, London, United Kingdom.
Recently we have described two cases of heterozygosity for the common
β°-thalassemia mutation β39 (C→T) presenting with a thalassemia
intermedia phenotype (1). Multiplex Ligation dependent Probe
Amplification (MLPA) analysis of the α-globin gene cluster revealed
two new rearrangements, consisting of a full duplication of the α-globin
genes locus including the upstream regulatory elements. Here, we
present two other case; one, a family of mixed Sephardic Ashkenazi
Jewish origin living in Canada, in which the propositus (a 2 yrs old girl)
presented with a pronounced microcytic hypochromic anemia, a borderline
HbA2 and heterozygous for a β polyA mutation. Only one parent
showed mild microcytic hypochromic anemia due to heterozygosity
for the β-mutation. The second case, a 6 yrs old girl of middle-eastern
origin living in the U.K., has severe anemia and splenomegaly, while
the mother from whom she has inherited the β 0 -thalassemia mutation
is clinically asymptomatic. MLPA analysis of the α-globin gene cluster
revealed two new rearrangements, consisting of a full duplication of
the α-globin gene cluster and the upstream regulatory elements. The
first is a duplication of approximately 435 kb between position 75563-
510533 from the telomere (UCSC Genome Browser, May 2004) and
the second, approximately 107 kb between positions 90548-198161.
We report the clinical and hematological data and the molecular
characterization. We conclude that α-globin gene duplication is more
common than previously thought and should be investigated as a contributing
cause in all unexplained unusually severe heterogeneous β
thalassemia.
(1) Harteveld et al. Blood Cells Mol Dis. 2008 May-Jun;40(3):312-6.
P02.180
α-Thalassemia: report on the last three years of activity
C. Curcio, C. Lodrini, A. Biasi, C. Melles, D. A. Coviello;
Medical Genetics Laboratory - Fondazione IRCCS, Ospedale Maggiore Policlinico,
Mangiagalli e Regina Elena., Milan, Italy.
α-Thalassemia is the most common of the inherited hemoglobin synthesis
disorders, which are the most common monogenic diseases. It
is characterized by decreased or complete absence of α-globin chain
synthesis, caused by deletion of or mutation in the α-globin genes.
Clinically, 4 variants of the syndrome are recognizable, with increasing
severity depending on how many normal α-globin genes are present
(3, 2, 1 or none). During the last three years of activity we have tested
109 individuals characterized by low MCV, normal or slightly reduced
Hb levels and normal HbA 2 .
Thirty single gene deletions (α 3.7), twenty one double gene deletions
(--SEA, --MED, --FIL, α 20.5) and 12 point mutations (Hb Icaria, Torino,
Constant Spring, Sun Praire, α2 init cd T>C, polyA) were analyzed by
Reverse Dot Blot and direct sequencing, and α thal mutations were
identified in 106 cases. In 12 individuals none of these mutations was
found.
The following genotypes were observed: α2 IVS 1-5 nt (12 subjects),
ααα (3), polyA/Hb Icaria (1), α 3.7/--MED (1), α 3.7/--SEA (1), α 3.7/-
-FIL (1), α 3.7/α2 init cd T>C (4), α 3.7/α 4.2 (1), α 3.7/α 20.5 (4), α
3.7/Hb Hasharon (2), α 3.7/Hb Torino (1), α 3.7/α2 IVS 1-5 nt (2), α
20.5/α2 IVS 1-5 nt (1).
Our study shows that the α 3.7 single gene deletion is a very frequent
cause of α-thalassemia in Italy but other mutations (--SEA, --MED, --
FIL, α 20.5) also seem to have acceptable frequencies.
P02.181
New observations and it‘s consequences on genetic
counselling: a case of β-Thalassemia and Hereditary
Hemochromatosis coexistence in homozigosity
N. Bukvic 1 , V. Longo 1 , R. Santacroce 1 , V. Bafunno 1 , M. Chetta 1 , G. D’Andrea 1 ,
M. Sarno 1 , F. Sessa 1 , F. Sportelli 2 , M. Roberti 2 , M. Margaglione 1,3 ;
1 Genetica Medica, Foggia, Italy, 2 II U.O. Medicina Trasfusionale, Azienda Ospedalo-Universitaria,
Foggia, Italy, 3 Unità di Emostasi e Trombosi, IRCCS, San
Giovanni Rotondo (FG), Italy.
Genetic counselling is an integral and expanding part of medical practice,
not only for those patients at risk, but also for patients with common
disorders with genetic component. Furthermore, together with a
fact of extreme velocity in application of new techniques and technologies
in a field of genetic testing procedures, make that sometimes a
role of genetic counsellor is completely forgotten.
Herein, we discussed some observations regarding double homozigosity
for two well studied illnesses [β-thalassemia (β-thal) and hereditary
hemochromatosis (HH)]. We reevaluate patients previously
characterized for: HBB (Hemoglobin beta locus) and HFE (major gene
associated with HH) respectively by our department. Our attention was
directed to an 18-year-old patient, who was a double homozygote for
β-thal [IVS1-110(G>A)/IVS1-110(G>A)] and HFE (H63D/H63D) who,
at 16 years of age, had cardiomyopathy with severe hypogonadism.
On the bases of results observed, it seems possible to suggest that
the HFE gene homozygous H63D mutation, which is responsible for
an adult onset of HFE, may be sufficient to provoke a juvenile hemochromatosis
phenotype, when in combination with β-thal homozygosity.
Even though, this observation open a possible “way” to speculate
regarding synergic (pejorative) effects of these two genes, it seems
extremely interesting to pay attention to possible cardiac problems,
especially for young β-thal patients with high iron overload and HH
homozygosity for mutation in the HFE gene. If confirmed, with further,
larger studies, this observation could be interesting from both points of
view i.e. clinician’s and counselor’s.
P02.182
molecular diagnostics of thalassemia intermedia in iran
M. Neishabury 1 , A. Azarkeivan 2 , C. Oberkanins 3 , F. Esteghamat 1 , N. Amirizadeh
2 , H. Najmabadi 1,4 ;
1 Genetics Research Center, University of Social Welfare and Rehabilitation
Sciences, Tehran, Islamic Republic of Iran, 2 Thalassemia Clinic and Research
Center, Iranian Blood Transfusion Organization (IBTO), Tehran, Islamic Republic
of Iran, 3 ViennaLab Diagnostics GmbH, Vienna, Armenia, 4 Kariminejad and
Najmabadi Pathology and Genetics Center, Tehran, Islamic Republic of Iran.
To improve the differentiation of thalassemia intermedia from other
hemoglobinopathies in Iran, four known genetic mechanisms_XmnI
Ggamma polymorphism, inheritance of mild and silent beta-thalassemia
alleles, delta beta deletion, and coinheritance of alpha- and betathalassemia_were
investigated in 52 Iranian individuals suspected
to have thalassemia intermedia based on clinical and hematological
characteristics. Beta globin mutations were studied using a reversehybridization
assay and sequencing of the total beta-globin gene. The
XmnI Ggamma polymorphism, the Sicilian delta beta deletion, and
four alpha-globin mutations (_a3.7, _a4.2, _MED, aaa anti-3.7) were
studied using PCR-based techniques. The inheritance of the XmnI
Ggamma polymorphism with severe beta-thalassemia alleles in the
homozygous or compound heterozygous state was the predominant
mechanism observed in 27 individuals (55.3%). In five cases, this status
overlapped with the _a3.7=aa genotype. The second most frequent
cause for thalassemia intermedia (14.8%) was the inheritance of mild
beta-thalassemia alleles, including IVS-I-6 (T>C), _88 (C>A), and +
113 (A>G). In three subjects (4.3%) the Sicilian delta beta deletion was
identified. HbS in association with beta-zero-thalassemia was found
in three patients with thalassemia intermedia phenotype. In 11 cases
(21.3%) no causative genetic alteration could be identified. Our results
reflect the diversity underlying thalassemia intermedia, and the limitations
of the applied clinical, hematological, and molecular approaches
for correct diagnosis. Some of the unresolved cases will offer an opportunity
to discover additional molecular mechanisms leading to thalassemia
intermedia.