Iron deficiency anaemia is the most frequent form of anaemia and is generally acquired.
“Low-cost” diet; increased iron needs during childhood, pregnancy, or lactation; bleeding
from the gastrointestinal or urogenital tract; and gastric pathology constitute the main settings
leading to “classical” iron deficiency anaemia. The clinical observation of unexplained forms
of iron deficiency anaemia, together with growing evidence that we are dealing with inherited
disorders and advances in knowledge concerning iron metabolism, have led to the description
of a new group of diseases in hematology known as genetic forms of iron deficiency anaemia.
Mutations in the gene encoding DMT1, the genetic forms of sideroblastic anaemias (ie,
mutations in glutaredoxin 5, aminolevulinic acid synthetase 2, and ABCB7 genes),
atransferrinaemia, the deficiency of ceruloplasmin, and the recently described mutations in the
matriptase-2 [TMPRSS6] gene comprise this new entity of iron deficiency anaemia.
The main characteristics of families described with iron deficiency anaemia secondary to a
mutation in the gene encoding DMT1 are the early appearance of severe microcytic,
hypochromic anaemia (usually at birth) and high serum iron and transferrin saturation with
low or normal ferritin levels. Because heme iron absorption is not disturbed, in nonvegetarian
humans, DMT1 mutations primarily affect iron utilization and not absorption.
The recently described mutation in the glutaredoxin 5 (GLRX5) gene leads to microcytic,
hypochromic anaemia with iron overload and the presence of ringed sideroblasts in the bone
marrow upon Perl’s staining. This is due to defective heme synthesis secondary to iron
regulatory proteins (IRPs) deregulation linked to the decreased production of iron-sulphur by
the mutated GLRX5. This mechanism operates at least partially in the other forms of
microcytic, congenital, or acquired sideroblastic anaemias as well.
The main characteristics of atransferrinaemia and aceruloplasminaemia are the presence of
moderate microcytic-hypochromic anaemia (late onset in the case of aceruloplasminaemia),
with low serum iron, liver iron overload, and high ferritin. In ceruloplasmin deficiency, brain
damage is found. Because transferrin is missing, there is reduced delivery of iron to bone
marrow erythroblasts leading to decreased haemoglobin synthesis. In aceruloplasminaemia,
there is a deficiency in ceruloplasmin, a ferroxidase. As a result, ferroportin can not release
iron to plasma transferrin, leading to iron deficiency anaemia with concomitant deposition of
iron to different organs (liver, pancreas, basal ganglia, etc).
The description by Beutler and colleagues of a transmembrane serine protease product of the
TMPRSS6 gene that interferes with hepcidin production led to the discovery of a severe form
of iron deficiency anaemia due to mutations in both paternal and maternal TMPRSS6 genes
that is refractory to iron treatment (Iron-Refractory, Iron-Deficiency Anaemia, or IRIDA
syndrome). At least nine families have been described with this syndrome. Affected members
suffer from a congenital severe hypochromic, microcytic anaemia with low serum iron and low transferrin saturation. The most pathognomonic finding is high hepcidin levels in serum
and urine of these patients, despite severe iron deficiency. There is no response to oral iron
and slight response to intravenous iron administration.
Although these genetic forms of iron deficiency anaemia are rare, haematologists should be
aware of their existence when investigating microcytosis of unknown origin, in cases of
peculiar forms of iron deficiency anaemia refractory to classical oral or intravenous iron
administration, or forms combining iron deficiency anaemia with iron overload of different
parenchyma organs. These forms of genetic iron deficiency anaemia are excellent models to
further increase our knowledge concerning iron metabolism and erythropoiessis……
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