Hyperferritinaemia in the absence of iron overload.

Abstract

Serum ferritin is normally a marker of iron overload. Ferritin genes are sited at chromosomes 19 and 11. Regulation of ferritin synthesis involves an interaction between an iron regulatory protein (IRP) and part of the ferritin mRNA designated the iron regulatory element (IRE). A disorder of ferritin synthesis resulting in hyperferritinaemia in the absence of iron overload has been described recently.
Hyperferritinaemia in the absence of iron overload was detected in a patient who was investigated for possible haemochromatosis. Serum iron, transferrin saturation, and ferritin concentration were studied in 11 members of this patient's family from three generations. Eight members had DNA samples analysed by direct cycle sequencing of the 5' untranslated region of the L ferritin gene.
Six of the family members studied had serum ferritin concentrations greater than 900 micrograms/l. However, serum iron and transferrin saturation were normal in these subjects who all had evidence of cataracts. Three affected family members who had genetic studies of the L ferritin gene on chromosome 19 had an A to G point mutation which was not found in unaffected members.
There was complete concordance between a mutated IRE, cataracts, and hyperferritinaemia in three generations of this family. This family study confirms the finding that hereditary hyperferritinaemia in the absence of iron overload is an autosomal dominant inherited disorder.

Full text

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CASE REPORTS
Hyperferritinaemia in the absence of iron overload
J D Arnold, A D Mumford, J O Lindsay, U Hegde, M Hagan, J R Hawkins
Abstract
Background—Serum ferritin is normally
a marker of iron overload. Ferritin genes
are sited at chromosomes 19 and 11.
Regulation of ferritin synthesis involves
an interaction between an iron regulatory
protein (IRP) and part of the ferritin
mRNA designated the iron regulatory ele-
ment (IRE). A disorder of ferritin synthe-
sis resulting in hyperferritinaemia in the
absence of iron overload has been de-
scribed recently.
Patientsandmethods—Hyperferriti-
naemia in the absence of iron overload
was detected in a patient who was investi-
gatedforpossible
Serum iron, transferrin saturation, and
ferritin concentration were studied in 11
members of this patient’s family from
three generations. Eight members had
DNA samples analysed by direct cycle
sequencing of the 5' untranslated region of
the L ferritin gene.
Results—Six of the family members stud-
ied had serum ferritin concentrations
greater than 900 µg/l. However, serum
iron and transferrin saturation were nor-
mal in these subjects who all had evidence
of cataracts. Three aVected family mem-
bers who had genetic studies of the L
ferritin gene on chromosome 19 had an A
to G point mutation which was not found
in unaVected members.
Conclusions—There was complete con-
cordance between a mutated IRE, cata-
racts, and hyperferritinaemia in three
generations of this family. This family
study confirms the finding that hereditary
hyperferritinaemia in the absence of iron
overload is an autosomal dominant inher-
ited disorder.
(Gut 1997; 41: 408–410)
haemochromatosis.
Keywords:
haemochromatosis; cataract; iron overload
ferritin; hyperferritinaemia;hereditary
The iron storage protein ferritin is synthesised
in the liver and diVerent proportions of the
component L (19 kDa, light) and H (21 kDa,
heavy) subunits give rise to isoferritins with tis-
sue specific distributions.1The L ferritin and H
ferritin genes are sited at chromosomes 19 and
11, respectively.2
Transferrin is the main iron transport
protein. Cellular iron homoeostasis is main-
tained by regulation of ferritin synthesis in
coordination with transferrin receptor expres-
sion. Ferritin synthesis can also be stimulated
as part of an acute phase response by cytokines
such as tumour necrosis factor ? and inter-
leukin 1?.3
Regulation of ferritin synthesis involves an
interaction between an iron binding protein
termed the iron regulatory protein (IRP) and
the ferritin mRNA.4IRP contains an iron–
sulphur complex and in iron deficient cells it
functions as an RNA binding protein; in iron
replete cells it functions as an aconitase, an
enzyme in the Krebs cycle.
A constant region of the mRNA molecule,
termed the iron responsive element (IRE),5–7
binds withIRP. The
complex inhibits ribosomal binding to mRNA
and prevents translation of the ferritin coding
sequence. A critical CAGUGU sequence
within IRE is important for binding with IRP.
When there is iron overload, as in hereditary
haemochromatosis, the IRE–IRP inhibitory
system is suppressed and ferritin synthesis is
increased. When this form of iron storage is
saturated, iron is deposited as haemosiderin in
tissue.8Relatives of patients with hereditary
haemochromatosis may have elevated serum
ferritin values without clinical evidence of
tissue iron deposition.9In hereditary haemo-
chromatosis about 83% of aVected individuals
have a mutated gene on chromosome 6
designated the HLA-H gene.10
We report on a family with high serum ferri-
tin values associated with early onset cataracts.
AVected family members showed no clinical
evidence of hereditary haemochromatosis or
iron overload.
resultant IRE–IRP
TABLE 1
and cataracts
Relation between serum ferritin concentrations
Family
member
Serum ferritin
(µg/l)
Transferrin
saturation Cataract
I1
I2
II1
II4
II5
III1
II2
II3
III2
III3
938
1449
1420
988
1452
902
37
49
18
17
22
17
26
37
21
NA
16
NA
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
15
19
Gut 1997; 41: 408–410408
Departments of
Gastroenterology,
Haematology, and
Ophthalmology, Ealing
Hospital, Southall, UK
J D Arnold
A D Mumford
J O Lindsay
U Hegde
M Hagan
Department of
Paediatrics,
Addenbrooke’s
Hospital, Cambridge,
UK
J R Hawkins
Correspondence to:
Dr J Arnold, Consultant
Gastroenterologist, Ealing
Hospital NHS Trust,
Uxbridge Road, Southall,
Middlesex UB1 3HW, UK.
Accepted for publication
20 February 1997

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Case report
A 25 year old woman was referred to the
gastroenterology clinic for investigation of pos-
sible haemochromatosis following the detec-
tion of raised serum ferritin at 1420 µg/l. She
was born with cerebral palsy and complained
of tiredness and brittle nails. She normally
attends a learning disability clinic and since her
symptoms suggested anaemia, haemoglobin
and ferritin were measured. The unexpected
ferritin result had prompted referral to our
gastroenterology clinic. She had a history of
cataracts, as did several members of her family.
She was found to have a raised serum ferritin
on three separate occasions despite normal
haemoglobin, liver and renal function, and
acute phase reactants (serum ferritin was
measured using a standard solid phase,two site
chemiluminescent immunometric assay (Im-
mulite)). Her karyotype was normal and HLA
haplotype was A2B44. Initial screening investi-
gations in other family members revealed that
her mother (I1) and her maternal aunt (I2) had
notably elevated serum ferritin with no other
markers of iron overload (table 1 and fig 1).
Liver biopsies on these two family members (I1
and I2) were done to examine for tissue iron
overload. These showed no evidence of excess
iron. All three family members (I1, I2, and II1)
had one unit of blood each venesected on suc-
cessive weeks. They developed iron deficiency
anaemia with reduced serum iron but contin-
ued to have raised serum ferritin concentra-
tions.
Three other family members (fig 1 and table
1) also had raised ferritin values.Blood samples
from family members were analysed for genetic
mutation within the L ferritin IRE.
POLYMERASE CHAIN REACTION AMPLIFICATION
AND DNA SEQUENCING
DNA (extracted from red and white blood
cells) from patient I2 was amplified by using
the polymerase chain reaction (PCR) as
described previously.11
were 5'-AGAAGCCGCCCTAGCCACGT-3'
(forward) and 5'-GAGCTAACCACAAAAA
CGGTGC-3' (reverse). The PCR product was
electrophoresed on an agarose gel and the
amplification fragment electroeluted.The frag-
ment was reamplified under the same condi-
tions, but using a nested reverse primer:
5'-GGTCCCAGAAGCAGGAGATG-3'. The
resulting amplification product was electro-
eluted and ethanol precipitated. The fragment
was dissolved in water and sequenced on both
strands using the ABI PRISM AmpliTaq FS
dye terminator cycle sequencing ready reaction
kit (Perkin Elmer) under the manufacturer’s
recommended conditions.
Primer sequences
ALLELE SPECIFIC OLIGONUCLEOTIDE
HYBRIDISATION
DNA samples were amplified with the forward
and reverse primers. Amplification products
were immobilised onto “Gene-Screen +”
membrane (DuPont) and probed as described
previously.12The primer sequences were 5'-
TGCTTCAACGGTGTTTGGA-3' (mutant
specific) and 5'-TGCTTCAACAGTGTTT
GGA-3' (wild type).
Direct cycle sequencing of the 5' untrans-
lated region of the L ferritin gene revealed that
subject I2 was heterozygous for an A to G point
mutation at position +40. This corresponded
to position 2 of the CAGUGU motif within the
L ferritin IRE. Allele specific oligonucleotide
hybridisation confirmed the presence of the
mutation in two further aVected family mem-
bers studied (subjects II1 and II5); this was
absent from all of the five unaVected family
members (subjects II2, II3, II6, III2, III3) who
were studied.
Each family member underwent an ophthal-
mic examination by a consultant ophthalmolo-
gist (MH). Results were normal in those with
normal ferritin levels, whereas all aVected fam-
ily members had anterior and posterior sutural
opacities (fig 2). The older members (I1 aged
62, and I2 aged 54) also had peripheral opaci-
ties of varying extent and density. The periph-
eral opacities had a radial orientation and were
more prominent near the equator of the lens.
The appearance was as clear fluid vacuoles
Figure 1:
with ferritin in excess of 900 µg/ml;symbols with crosses indicate ferritin concentrations
within the normal range;clear symbols indicate spouses in whom the ferritin concentrations
have not been measured.
Family tree of the patients with hyperferritinaemia.Solid symbols indicate those
Figure 2:Cataract in patient I2.
Hyperferritinaemia in the absence of iron overload
409

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between lens fibres in the cortical zone. They
did not seem to interfere greatly with visual
acuity.
Discussion
This is the first report of an English family with
autosomal dominant inheritance of hyperferri-
tinaemia associated with premature cataracts.
Our patients had normal transferrin satura-
tions and showed no histological evidence of
increased iron deposition in the liver.
The abnormal phenotype in our family was
associated with heterozygosity for an A to G
point mutation in the L ferritin gene. This cor-
responded to position 2 of the conserved
CAGUGU nucleotide motif in the mRNA
IRE. This mutation was absent in unaVected
family members. The base substitution in this
region disrupts the site specific binding be-
tween IRE and IRP thereby reducing the sup-
presser influence on L ferritin mRNA transla-
tion.Increasedferritin
independent of cellular iron status.
Inherited hyperferritinaemia without iron
overload has previously been reported in three
continental families, all with similar inherit-
ance pattern to our patients.13 14In a family
study reported from Italy, hyperferritinaemia
was associated with a G to C substitution at
position 3 of the CAGUGU IRE motif.15In
another report from France aVected members
were found to have an A to G substitution in
position 2.16This is an identical substitution to
that in our patients.
The only clinical manifestation in these
patients seems to be early onset cataracts.
However, the structure of the sutural cataracts
described here diVers from the pulverulent
type described in the French family.14Heredi-
tary cataracts are a heterogeneous group of
disorders that may result from abnormal
expression of genes encoding lens specific
proteins.17 18However, it is diYcult to envisage
how the point mutation in the L ferritin gene
could result in abnormal expression of an
unrelated lens protein gene. A more likely
explanation is that the cataracts in our patients
represent deposits of L ferritin subunits.Serum
ferritin should be measured routinely in
children with developmental cataracts.
“Sunflower” cataract due to deposition of
copper is a rare but recognised finding in Wil-
son’s disease.19It is unclear as to why cataracts
are common in hereditary hyperferritinaemia
but a rare finding in hereditary haemochroma-
tosis. It is possible that tissue specificity of iso-
ferritins found in hereditary hyperferritinaemia
may be diVerent to that in hereditary haemo-
chromatosis.
In contrast to patients with hereditary
haemochromatosis, transferrin saturation is
normal in hereditary hyperferritinaemia. A
syndrome of non-hereditary liver iron overload
in patients with modestly raised serum ferritin
synthesis occurs
but normal transferrin saturation was reported
recently.20This disorder is distinct from both
hereditary haemochromatosis and hereditary
hyperferritinaemia and seems to be associated
with hyperlipidaemia and impaired glucose
tolerance.20
Transferrin saturation and serum ferritin
measurements are used as screening tests for
hereditary haemochromatosis,9but caution
should be exercised in the interpretation of
raised ferritin values.
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