12th Congress of the European Hematology ... - Haematologica

12 th Congress of the European Hematology Association
expression of CD47, CD35 and CD55 on RBCs and SIRP-α,β on monocytes
of active AIHA patients, AIHA in remission and healthy controls
were not statistically different. Active AIHA patients showed significant
lower CD59 expression on RBCs than healthy controls, while CD59
expression in patients whit AIHA in remission was not significantly different
from that of healthy controls (Table 1). Four patients presenting
life threatening AIHA were treated with high dose of steroids and RBC
transfusions, but three patients evolved to death. The expression of
CD59 on RBCs of 3 AIHA patients who died were significantly lower
than that seen on RBCs healthy controls (MFI=433.6±69.6 and
553.74±36.6, p=0.0001). Although experimental studies have suggested
that CD47 has a profound influence on the severity of AIHA in mice,
by binding of RBC CD47 to SIRP-α on macrophages, the present human
data do not demonstrate significant difference on RBCs of patients warm
AIHA or healthy individuals. On the other hand, complement regulatory
proteins (CD35, CD55 and CD59) may play an important role in protecting
RBC destruction through the activation of complement. Our
results suggest that patients with active wAIHA may present significant
CD59 deficiency on their RBCs that may increase the susceptibility of
cells to complement-mediated lysis resulting in severe clinical hemolysis.
(Funding by FAPESP).
Table 1.
0792
IDENTIFICATION OF A NOVEL TRUNCATING MUTATION OF HEMOJUVELIN (HFE2) GENE
LEADING TO SEVERE JUVENILE HEMOCHROMATOSIS
A. Gilles, C. Rydlewski, F. Devuyst, A. Kentos, M.J. Abramowicz,
G. Vassart, J. Parma
Hopital Erasme ULB, BRUSSELS, Belgium
Background. Juvenile hemochromatosis ( JH) is a rare and devastating
disorder of iron metabolism leading to severe and early end organ damage
threw iron overload. Homozygous mutations of HFE2 and less frequently
HAMP gene lead to early onset severe hemochromatosis. The
function of hemojuvelin is not perfectly elucidated. It is accepted that HJ
positively modulates the iron regulator hepcidin. We report the case of
a 26 year old north african male consulting for erectile dysfonction. With
hypogonadotropic hypogonadism. Serum ferritin level was 5069 ng/mL
and transferrin saturation > 90% leading to high suspiscion of
hemochromatosis. Hepatic MRI assessed hepato- pancreatic iron overload
and liver biopsy showed evidence of cirrhosis.No diabetes was
diagnosed. Cardiac MRI showed ventricular hypertrophy and muscular
iron deposits without contractile dysfunction. Methods and Results.
Genetic testing was performed but failed to identify mutation neither
of the HFE nor the HAMP gene. Direct sequencing of the 3 coding exons
of the HFE2 ( hemojuvelin) gene displayed homozygous p.Arg257 X
(g.3147 C>T) mutation. The genomic reference sequence is
NC_000001.8. Discussions. This mutation has not been reported yet ,
nevertheless, out of it’s truncating nature it can be considered responsible
for the clinical presentation. Truncating mutations account for 50%
of the HFE2 mutations. Our patient underwent hormonal substitution,
weekly 500 ml phlebotomy and daily iron chelation with deferrioxamine.
After 18 weeks of treatment , SFL was still 2505 ng/mL and TfSat
>90% with elevated hepatic enzymes accounting for the dramatic iron
overload and the severity of the underlying iron metabolism disorder.
Conclusions. we describe a novel homozygous truncating mutation
p.arg257X (g.3147 C>T) mutation of the HFE 2 (hemojuvelin ) gene leading
to severe juvenile hemochromatosis with multiple end organ damage
consecutive to iron overload.
296 | haematologica/the hematology journal | 2007; 92(s1)
0793
TRIOSE-PHOSPHATE ISOMERASE DEFICIENCY: MOLECULAR STUDIES IN TWO PATIENTS
L. Manco, 1 J. Vidán, 1 L. Relvas, 1 J. Azevedo, 1 F Neves, 2 M.L. Ribeiro1 1 2 Centro Hospitalar de Coimbra, COIMBRA; Hospital Pediátrico, COIMBRA,
Portugal
Background. Triosephosphate isomerase (TPI, EC 5.3.1.1) catalyzes the
reversible isomerisation of dihydroxyacetone phosphate (DHAP) and
glyceraldehyde-3-phosphate (G-3-P). TPI deficiency is the most severe
autosomal recessive disorder of the glycolytic pathway associated with
neonatal jaundice, chronic haemolytic anaemia, progressive neuromuscular
dysfunction and increase propensity to infection. Almost all reported
cases are of European origin (15/18) and lethality was common in early
childhood. To date 14 different mutations in the human TPI gene
have been identified. The most frequent, 11 out of 14 (79%) mutant
alleles, is the 315G>C mutation at exon 3 leading to the amino acid
change 104Glu>Asp. This mutation has been found in apparently unrelated
families all over the world, in contrast to the other known TPI
mutations reported in individual families. Aims. To establish the molecular
basis of TPI deficiency in 2 patients. Patients. Case 1: Full-term
female newborn with severe haemolytic anaemia requiring exchange
transfusion and temporary assisted ventilation. Erythrocyte TPI activity
was 31% of normal. The parents were unrelated and healthy, of Spanish
origin, both with erythrocyte TPI activity around 60%. At the age
of one month presented with seizures and severe respiratory failure,
dependent of assisted ventilation, and died at age of 50 days. Case 2: A
33 weeks premature newborn male with severe haemolytic anaemia
and respiratory distress. Erythrocyte TPI activity was markedly reduced
(45% of normal, but in the presence of transfused donor erythrocytes).
The parents, of Portuguese origin, were unrelated; they did not present
clinical symptoms but TPI activity was 44% and 35% of normal. The
patient became transfusion dependent and developed progressive neurological
(especially motor) impairment which progressed to respiratory
failure, needing assisted ventilation by the third year of life. He died
at the age of three years. Methods. After informed consent, genomic
DNA was extracted from peripheral blood samples. The entire coding
sequence and adjacent regions of TPI gene were amplified by PCR and
sequenced. Results. Propositus 1: TPI gene sequencing showed compound
heterozygosity for the common 315G>C (E104D) mutation and
a previously unknown mutation in exon 2, the transversion 188C>A
predicting the amino acid change 62Ala>Asp. Sequencing of the entire
TPI coding regions and splicing site boundaries did not showed any other
nucleotide mutations. Screening for mutation 188A in 50 healthy controls
was negative. Both parents sequencing confirmed the presence of
the 315C allele in the mother and the 188A allele in the father. Propositus
2: TPI gene exon 3 sequencing demonstrated a homozygous 315G>C
(E104D) mutation. Conclusions. In 2 unrelated TPI deficient patients the
most frequent TPI mutation E104D was found in 3 alleles. The importance
of Glu104 to enzyme structure and function was indicated by its
conservation in the TPI protein of all species characterized to date. The
other mutation, 188C>A, previously not described, predicts a drastic
non-conservative replacement of the nonpolar Ala by the acidic Asp at
residue 62. The evolutionary conservation of Ala62 from C. elegans to
humans indicates that this mutation certainly influences the TPI conformation,
stability or kinetic properties, reducing the enzymatic activity.